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PDP-9 supervisory programs for the data-linkage to IBM 360/67 Ng, Nam 1970

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PDP-9 SUPERVISORY PROGRAMS FOR THE DATA-LINKAGE •  TO IBM 360/67  by NAM NG  B.Sc.  (Eng.) U n i v e r s i t y o f Hong Kong, 1967  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS OF THE DEGREE OF  MASTER OF APPLIED SCIENCE  in  the Department of  Electrical  We  accept  this  Engineering  t h e s i s as conforming to the  • r e q u i r e d standard  Research S u p e r v i s o r Members o f the Committee .,  A c t i n g Head o f the Department  Members o f t h e Department of  Electrical  Engineering  THE UNIVERSITY OF BRITISH COLUMBIA  August, 1970  In  presenting  this  an a d v a n c e d d e g r e e the L i b r a r y I  further  for  of  this  written  at  agree  freely  that permission  for  It  financial  of  Columbia,  British for  gain  Columbia  the  requirements  reference copying of  I agree and this  shall  that  not  copying  or  for  that  study. thesis  by t h e Head o f my D e p a r t m e n t  i s understood  Department  Date  of  for extensive  permission.  The U n i v e r s i t y o f B r i t i s h V a n c o u v e r 8, Canada  fulfilment  available  p u r p o s e s may be g r a n t e d  representatives. thesis  in p a r t i a l  the U n i v e r s i t y  s h a l l make i t  scholarly  by h i s  thesis  or  publication  be a l l o w e d w i t h o u t  my  ABSTRACT  PDP-9 programs are p r o v i d e d  f o r the i n t e r - c o m p u t e r  PDP-9 i n the Department o f E l e c t r i c a l E n g i n e e r i n g Computing Centre o f the U n i v e r s i t y o f B r i t i s h communication p r o c e d u r e used are d e s c r i b e d . recovery  i s incorporated  the IBM  360/67.  I t a l s o allows  D e t a i l s o f the data-phone h a n d l e r are g i v e n i n the  Columbia.  D e t a i l s of  t r a n s f e r s between the  r o u t i n e and  Appendix.  i  the  Automatic e r r o r d e t e c t i o n  the PDP-9 as a c o n v e r s a t i o n a l  file  the  360/67 i n the  to ensure c o r r e c t message t r a n s m i s s i o n s .  "TRSFER" has been w r i t t e n to o p e r a t e to  to the IBM  linkage of  two  and  A program terminal computers.  o p e r a t i o n o f the program "TRSFER"  TABLE OF CONTENTS Page ABSTRACT  i  TABLE OF CONTENTS  i i  LIST OF ILLUSTRATIONS  iv  ACKNOWLEDGEMENT  v  1.  INTRODUCTION  1  2.  COMMUNICATION PROCEDURES  4  2.1  Communication Code  4  2.2  Message Format  4  2.3  Message T r a n s f e r C o n t r o l Procedures  6  2.4  E r r o r D e t e c t i o n and E r r o r Recovery Procedures  7  3.  4.  PROVISIONS MADE FOR THE PDP-9  12  3.1.1  The Data-Phone H a n d l e r  12  3.1.2  The Macros  13  3.1.3  Data Modes  14  3.1.4  E r r o r D i a g n o s t i c Messages  14  3.1.5  The H a n d l e r R o u t i n e  15  3.2  The Program "TRSFER"  15  3.2.1  O p e r a t i o n as a T e r m i n a l T e l e t y p e  3.2.2  Data F i l e T r a n s f e r s  . . .  15 17  DISCUSSION  19  APPENDIX I  T a b l e o f USASCII Codes f o r Inter-computer Communication . .  21  APPENDIX I I  The Data-Phone H a n d l e r  22  . . . . .  ii  Page  APPENDIX I I I  The Macros  24  APPENDIX IV  Data T r a n s m i s s i o n Paths  APPENDIX V  E r r o r D e t e c t i o n and H a n d l i n g  APPENDIX VI  D e t a i l e d Flow-Charts  APPENDIX V I I  The Program "TRSFER"  42  APPENDIX V I I I  D e t a i l e d Flow-Charts f o r the Program "TRSFER"  45  . . . . . . . .  f o r the H a n d l e r R o u t i n e  REFERENCES . ,  33 35 . . . . . . .  37  48  iii  L I S T OF ILLUSTRATIONS Page  F i g . 1.  O v e r a l l View o f the Communication L i n k a g e between PDP-9 and the  IBM 360/67  2  F i g . 2.  T y p i c a l Communication Message Format  F i g . 3.  G e n e r a l F l o w - c h a r t f o r the Message  Communication Scheme  ....  8  F i g . 4.  Schematic F l o w - c h a r t f o r the data-phone h a n d l e r r o u t i n e  . . .  16  F i g . 5.  Schematic F l o w - c h a r t f o r the program TRSFER  iv  .  4  18  ACKNOWLEDGEMENT  I would l i k e  to express my g r a t i t u d e to my s u p e r v i s o r , . D r . G.F.  Schrack, f o r h i s c o n s t a n t ' o f the p r o j e c t . the  advice  and encouragement d u r i n g  I would a l s o l i k e  t h e s i s and h i s v a l u a b l e  to thank Dr. J . S . MacDonald f o r  Mr.  to Mr. W. D e t t w i l e r o f the Computing  f o r t h e i r co-operation  during  the e x p e r i m e n t s , and to  G. A u s t i n f o r h i s t e c h n i c a l a s s i s t a n c e . Thanks to Mr. C.Y. Suen and Mr. N. Borowski f o r p r o o f  t h e s i s , and e s p e c i a l l y  to M i s s Heather DuBois f o r t y p i n g  Financial assistance (No.  reading  comments.  A note o f a p p r e c i a t i o n i s given Centre and h i s s t a f f  the whole c o u r s e  r e a d i n g the  the m a n u s c r i p t .  through N a t i o n a l Research C o u n c i l Grant  67-0148) and a U n i v e r s i t y o f B r i t i s h Columbia Graduate F e l l o w s h i p i s  gratefully  acknowledged.  v  1.  INTRODUCTION  With the development o f t i m e - s h a r i n g  computers, and  the f a s t growing  v a r i e t y o f d a t a p r o c e s s i n g a p p l i c a t i o n s , the demand f o r d i g i t a l d a t a has  been e v e r i n c r e a s i n g .  I t b r o u g h t about the i n t e r c o n n e c t i o n o f  computers, e s p e c i a l l y s m a l l s c i e n t i f i c c e n t r a l time-sharing c a t e w i t h , and For  computers, e n a b l i n g u s e r s a t one  reasons,  o f the o t h e r  computer.  360/67 of the Computer C e n t r e .  users o f the PDP-9 to communicate w i t h c a p a c i t y and  i n s t a l l a t i o n to communi-  the PDP-9 computer o f the Department o f  E n g i n e e r i n g i s l i n k e d to the IBM  large storage  the IBM  f a s t computational  360/67, and  c a r r i e d out on  and  cables.  Two  a b i l i t y o f the IBM  essentially  the advantage o f r e d u c i n g which s e r v e s  procedures  follow closely  Standard). is built  360/67.  With  as a h a l f - d u p l e x system.  transmission e f f i c i e n c y i n a s t a n d a r d i z e d way.  those o f USASCII standards"*"  f o r Information  Hardware has  for transmission, the  However, t h e r e i s  still  and  considerably. Communication code (United States  and  of  I n t e r c h a n g e ) — n o w the ANS(American N a t i o n a l  been purchased from The  a c c o r d i n g to the EIA Transmission  c a b l e s a r e used, one  voice-grade  F u l l - d u p l e x t r a n s m i s s i o n i s p o s s i b l e , but  l i n k a g e operates  America Standard  the  time used i n l i n e r e v e r s a l s i n h a l f - d u p l e x systems,  to i n c r e a s e the  The  enables  a p p l i c a t i o n s can  computers i s made over  p a i r s o f telephone  the o t h e r f o r r e c e p t i o n .  l i n k a g e operates  This  the PDP-9.  Communication between the two telephone  Electrical  to make use o f  t h i s l i n k a g e e s t a b l i s h e d , more s o p h i s t i c a t e d d a t a - p r o c e s s i n g be  different  computers at remote l o c a t i o n s to l a r g e  to make use o f the f a c i l i t i e s these  transmission  D i g i t a l Equipment Corp.  and  2  ( E l e c t r o n i c I n d u s t r i e s A s s o c i a t i o n ) Standards .  r e c e p t i o n o f d a t a f o l l o w b i n a r y synchronous  con-  3 ventions  .  Data i s t r a n s m i t t e d s e r i a l - b y - b i t  r e c e p t i o n o f data depends on  b i t and  and  serial-by-character.  c h a r a c t e r s y n c h r o n i z a t i o n of  both  Correct  stations.  This i s achieved  a t the b e g i n n i n g  o f each t r a n s m i s s i o n by t r a n s -  m i t t i n g a s y n c h r o n i z a t i o n p a t t e r n , and once s y n c h r o n i z e d , i s maintained The  until  the end o f the t r a n s m i s s i o n .  two computers are l i n k e d t o g e t h e r i n such a way t h a t the PDP-9  e s s e n t i a l l y operates transmission  as a c o n v e r s a t i o n a l t e r m i n a l to the IBM 360/67.  r a t e i s 2400 b i t s p e r s e c .  Due to the data p r o c e s s i n g  o f the PDP-9, d a t a r e c e i v e d a t the PDP-9 can be p r o c e s s e d sent  the c h a r a c t e r phase  to the IBM 360/67.  before  However, because the IBM 360/67 i s a  computer and there i s no p r i o r i t y  Data ability  they are  time-sharing  f o r d a t a communication o v e r the l i n k a g e ,  r e a l time d a t a communication i s n o t p o s s i b l e .  To ensure c o r r e c t n e s s o f d a t a  r e c e i v e d , automatic e r r o r r e c o v e r i e s by r e t r a n s m i s s i o n are i n c o r p o r a t e d . An o v e r a l l view o f the communication l i n k a g e between the two computers  i s shown i n F i g . 1.  The PDP-9 i s connected to the communication  system v i a the data-phone DP09A  IBM 360/67  Multiplexer  PDP-8  4  from the D i g i t a l Equipment C o r p o r a t i o n .  Data phone  Data set  it  Data set  The  DP09A  Telephone cables  COMPUTING  CENTRE  Fig. 1  ELECTRICAL ENGINEERING DEPARTMENT  O v e r a l l view o f the communication l i n k a g e between PDP-9 and IBM 360/67  DP09A i s a b i n a r y synchronous f u l l - d u p l e x communication channel f o r i n t e r c o n n e c t i n g the P D P - 9 to the data s e t v i a the i n p u t - o u t p u t  i n t e r f a c e o f the P D P - 9 .  I ti s  essentially  a s e r i a l - p a r a l l e l b i n a r y data c o n v e r t e r .  accumulator  are t r a n s f e r r e d  i n t o a s e r i a l b i n a r y stream. to the IBM  to the DP09A v i a the I/O bus, where i t i s c o n v e r t e d I t i s then t r a n s m i t t e d . o v e r telephone  360/67 v i a the d a t a s e t .  modems, are b u i l t  Data from the PDP-9  The  d a t a s e t s , t e c h n i c a l l y known as  a c c o r d i n g to the EIA s t a n d a r d s .  s e t a r e t r e a t e d i n a r e v e r s e manner.  cables  Data r e c e i v e d from  They a r e f i r s t assembled to form  the d a t a parallel  8 - b i t c h a r a c t e r s i n the d a t a phone b e f o r e they a r e t r a n s f e r r e d to the PDP-9 accumulator  v i a the I/O  bus.  At the computing c e n t r e end, i n the PDP-8. o f the IBM  d a t a are t r e a t e d i n a s i m i l a r manner  But, b e f o r e the d a t a a r e t r a n s f e r r e d to the c e n t r a l p r o c e s s i n g u n i t  360/67 v i a the m u l t i p l e x e r , a code c o n v e r s i o n i s n e c e s s a r y s i n c e  the communication code f o r the two DEC-computers i s USASCII code whereas the IBM  360/67 works w i t h EBCDIC code (extended b i n a r y - c o d e d - d e c i m a l  interchange  code) . The  two  computers are l i n k e d by d e d i c a t e d l i n e s .  can communicate w i t h the IBM The p r o c e d u r e  used  360/67 a t any  time when the l a t t e r i s o p e r a t i o n a l .  f o r t h i s l i n k a g e i s s i m i l a r to any  t e r m i n a l s o f the IBM  360/67.  Users o f the PDP-9  of the o t h e r remote  2.  2.1  Communication  COMMUNICATION  PROCEDURES  Code  The USASCII code i s used as the communication code. the codes i s shown i n Appendix I .  Each communication  A table of  c h a r a c t e r i s formed  from the seven b i t s USASCII code w i t h a p a r i t y b i t as the e i g h t h b i t . p a r i t y , as s u g g e s t e d by USASCII s t a n d a r d s on communication S i n c e the data-phone D P 0 9 A i n s t a l l e d w i t h synchronous i d l e c h a r a c t e r s , the l o g i c a l modified  2.2  Odd  codes"', i s used.  the P D P - 9 works w i t h even p a r i t y c i r c u i t r y o f the D P 0 9 A has been  to make i t c o m p a t i b l e w i t h the communication  system.  Message Format  I n d e c i d i n g the message format, the proposed s t a n d a r d s have been followed  closely.  However, s l i g h t  d i s c r e p a n c i e s are i n e v i t a b l e .  A  typical  communication message i s shown i n F i g . 2.  s S S S S S S Y Y Y Y 0 E T N N N N H L X Fig. 2  To i n i t i a t e  T E X T  E B TT C Q X C  T y p i c a l communication message format  transmission,  the t r a n s m i t t i n g s t a t i o n sends a number of-  i n t h i s system, f o u r — s y n c h r o n o u s i d l e c h a r a c t e r s w i t h the r e c e i v i n g s t a t i o n . S t a r t o f Heading c h a r a c t e r  Following (SOH)  to e s t a b l i s h s y n c h r o n i z a t i o n  the s y n c h r o n i z a t i o n p r o c e d u r e , the  i s transmitted.  T h i s i n d i c a t e s the s t a r t  o f the h e a d i n g o f the message. indication  o f the c o n t e n t  The h e a d i n g i s g e n e r a l l y i n t e n d e d  to g i v e some  o f the message and i s u s u a l l y n o t r e v e a l e d  to the  user. A Select Character  i s i n c l u d e d as the h e a d i n g o f t h e message, to  i n c r e a s e the e r r o r d e t e c t i n g a b i l i t y o f the communication scheme. character  can o n l y assume two v a l u e s , v i z . i n 7 b i t s o c t a l , 040 and 060, w i t h  p a r i t y i n c l u d e d as the e i g h t h b i t . with  the S e l e c t C h a r a c t e r  Consecutive  assuming these  t r a n s m i s s i o n be n e c e s s a r y ,  the S e l e c t C h a r a c t e r  o n l y i f the S e l e c t C h a r a c t e r  Character  alternately.  c o r r e c t and a c c e p t a b l e  v e r i f i c a t i o n on the proper  I t s h o u l d be n o t e d t h a t the two v a l u e s  chosen a r e q u i t e a r b i t r a r y .  Should r e -  assumes i t s l a s t v a l u e .  i s d i f f e r e n t from the one i n the l a s t  This procedure provides  messages r e c e i v e d .  messages a r e t r a n s m i t t e d  two v a l u e s  a message c u r r e n t l y r e c e i v e d i s c o n s i d e r e d  message.  This  Any two v a l u e s  Thus,  i f and accepted  sequence o f the  of t h e S e l e c t  c o u l d have been chosen.  6 In some systems  o n l y one b i t r a t h e r than one c h a r a c t e r  i s used f o r the  same p u r p o s e . The Character.  S t a r t o f Text  (STX) c h a r a c t e r i s t r a n s m i t t e d  f o l l o w i n g the S e l e c t  T h i s c h a r a c t e r i n d i c a t e s the end o f the h e a d i n g and the s t a r t o f  the a c t u a l message o r t e x t t h a t i s communicated. l i n e o f d a t a under the M i c h i g a n T e r m i n a l In terms o f punch c a r d mode, t h i s  The t e x t i s one complete  System (MTS) used by the IBM 360/67.  i s equivalent  to one c a r d image] and i n  t e l e t y p e mode, one l i n e o f t e x t up to CNTRL Q (+Q) o r c a r r i a g e r e t u r n .  The +Q  c h a r a c t e r i s always t r a n s m i t t e d a t the end o f the message. The by  text i s terminated  the B l o c k Check C h a r a c t e r  BCC i s a t e x t c h e c k i n g  (ETX) c h a r a c t e r ,  followed  (BCC, which i s a l s o known as b l o c k p a r i t y ) .  character.  o f the message, s t a r t i n g  by the End o f Text  The  I t i s formed by t a k i n g the sum (modulo 2)  from the c h a r a c t e r f o l l o w i n g the SOH c h a r a c t e r , i . e .  6  the S e l e c t C h a r a c t e r ,  up to and i n c l u d i n g the ETX c h a r a c t e r .  a l o n g i t u d i n a l b l o c k p a r i t y checking  character.  Block  formed a t b o t h ends o f the l i n k a g e i n d e p e n d e n t l y is  r e s p o n s i b l e f o r comparing them.  I d e n t i c a l c h a r a c t e r s i n d i c a t e t h a t the  Should the two be d i f f e r e n t ,  be i n c o r r e c t and r e q u e s t  Check C h a r a c t e r s a r e  and the r e c e i v i n g s t a t i o n  r e c e p t i o n has been e r r o r f r e e and w i l l be accepted detected.  I t thus a c t s as  i f no o t h e r e r r o r s a r e  the message r e c e i v e d i s c o n s i d e r e d to  f o r r e t r a n s m i s s i o n i s made.  A f t e r t r a n s m i t t i n g the BCC, an a l l zero b i t s c h a r a c t e r i s sent to i n d i c a t e the end o f the t r a n s m i s s i o n .  The r e c e i v i n g s t a t i o n can then  initiate  to send the acknowledgement o r r e p l y .  2.3  Message T r a n s f e r C o n t r o l P r o c e d u r e s  Though b a s i c a l l y h a l f - d u p l e x mode.  a f u l l - d u p l e x system, the l i n k a g e i s o p e r a t e d i n  Nevertheless,  there i s s t i l l  the advantage o f o b v i a t i n g the  need o f l i n e r e v e r s a l s , and t h i s a i d s to s i m p l i f y the communication c o n t r o l procedures. To i n i t i a t e  communication, the t r a n s m i t t i n g s t a t i o n sends a complete  l i n e o f message i n t h e format d e s c r i b e d above.  I t then w a i t s  f o r t h e acknowledgement from the o t h e r s t a t i o n . s t a t i o n searches is  initiated  f o r synchronous i d l e  and the acknowledgement i s examined.  the form o f two c o n s e c u t i v e characters (NAK). and with  characters.  identical  characters.  i n s e a r c h mode  W h i l e i n s e a r c h mode, the Once d e t e c t e d ,  data-reception  The acknowledgement i s i n The o n l y v a l i d  acknowledgement  a r e t h e P o s i t i v e Acknowledgement (ACK) and the N e g a t i v e Acknowledgement  An ACK i n d i c a t e s t h a t the l a s t message has been c o r r e c t l y  received,  the t r a n s m i t t i n g s t a t i o n can then p r o c e e d to t r a n s m i t a new l i n e o f message, the S e l e c t C h a r a c t e r  value  alternated.  t h i s manner u n t i l a l l messages have been  Message t r a n s f e r c o n t i n u e s i n  transmitted.  7  I f a NAK i s r e c e i v e d , i t i n d i c a t e s t h a t the l a s t not been c o r r e c t l y r e c e i v e d  and r e - t r a n s m i s s i o n  The message i s r e - t r a n s m i t t e d the  with  o f the message i s r e q u i r e d .  the S e l e c t C h a r a c t e r  value  u n a l t e r e d and  t r a n s m i t t i n g s t a t i o n w a i t s f o r the acknowledgement a g a i n .  re-transmissions  are attempted f o r e r r o r  error condition s t i l l  persists,  recovery  human i n t e r v e n t i o n i s n e c e s s a r y  An E n q u i r y  acknowledgement.  f o r each message.  I f the  Under such  An  circumstances,  f o r communication r e c o v e r y .  I f n e i t h e r ACK nor NAK i s r e c e i v e d , to be g a r b l e d .  Up to f i v e  the communication i s c a l l e d t o a h a l t .  e r r o r message i s p r i n t e d on the PDP-9 t e l e t y p e .  the  t r a n s m i s s i o n has  (ENQ) c h a r a c t e r  the acknowledgement i s assumed  i s sent  f o r a re-transmission of  Should t h i s o c c u r f o r more than f i v e  times, the communi-  c a t i o n i s again h a l t e d and human i n t e r v e n t i o n i s r e q u i r e d . A f t e r t r a n s m i t t i n g a l l messages, the t r a n s m i t t i n g s t a t i o n t e r m i n a t e s transmission  by s e n d i n g an End o f T r a n s m i s s i o n  (EOT) c h a r a c t e r .  i n r e c e i v e mode, g i v i n g up i t s r i g h t o f t r a n s m i s s i o n  I t then w a i t s  to the o t h e r s t a t i o n .  The message t r a n s f e r p r o c e d u r e i s q u i t e s y m m e t r i c a l f o r both s t a t i o n s . However, communication can o n l y be i n i t i a t e d by a r e q u e s t s i n c e the PDP-9 i s u s u a l l y i n a p a s s i v e cerned.  s t a t e as f a r as t h i s l i n k a g e i s con-  The IBM 360/67, on r e c e i v i n g the request,  message t r a n s f e r s .  from the PDP-9  F i g . 3 shows a f l o w - c h a r t  can p r o c e e d to i n i t i a t e  f o r the above p r o c e d u r e s  imple-  mented i n the l i n k a g e .  2.4  Error Detection  and E r r o r Recovery P r o c e d u r e s  I n e v i t a b l y , e r r o r s w i l l o c c u r d u r i n g message t r a n s m i s s i o n s . d e s i r a b l e to be able automatically  these e r r o r s and i f p o s s i b l e c o r r e c t them  w i t h o u t human i n t e r v e n t i o n .  are i n c o r p o r a t e d it  to d e t e c t  f o r such purposes.  i s not p o s s i b l e to d e t e c t  It i s  E r r o r d e t e c t i o n and r e c o v e r y  Though the scheme i s n o t p e r f e c t ,  schemes since  a l l e r r o r s , t h e p r o c e d u r e i s q u i t e s u f f i c i e n t to  Initiate  Transmission  Send new  text Alternate select character  Wait f o r acknowledgement  Send o l d t e x t w i t h o u t change  Must be t e x t check f o r e r r o r  Send l a s t acknowledgement  No  Send  NAK Output  text  •  Fig.  3.  G e n e r a l Flow-Chart o f the Message Communication Scheme  h a n d l e most of the e r r o r s . E r r o r s are d e t e c t e d characters  i n s e v e r a l ways.  are sampled a t p r o p e r  a f t e r s y n c h r o n i z a t i o n of the two imposed on d a t a r e c e p t i o n by  times,  To  ensure t h a t b i t s  and  r e c e p t i o n of data i s i n i t i a t e d  stations.  only  A "Time-out" r e s t r i c t i o n i s a l s o  the data-phone:  I f any b i t i s not  received 4  w i t h i n 1.5  b i t times,  the e n d f l a g i s s e t and  i n t e r r u p t s the computer  , indi-  c a t i n g the l o s s o f t r u e c h a r a c t e r phase. The  r e c e i v e d data i s t e s t e d f o r v e r t i c a l p a r i t y before  whether d a t a o r c o n t r o l c h a r a c t e r s . errors that occur  that occur  checking  to d e t e c t a l l odd  i n the seven b i t s o f each c h a r a c t e r .  tested for l o n g i t u d i n a l parity using errors  This serves  the BCC.  i n such a way  numbers of  The message i s f u r t h e r  This detects  i n any b i t p o s i t i o n o f the s e v e n - b i t  methods combined a c t t o g e t h e r  identification-  a l l odd  codes.  The  numbers of two  that e r r o r s are  parity  not  d e t e c t e d o n l y i f an even number o f e r r o r s have o c c u r r r e d b o t h v e r t i c a l l y each c h a r a c t e r i n the message and  logitudinally  for  f o r each o f the b i t p o s i t i o n s  o f the message. Checking by means of the l o g i c a l sequence of the d a t a r e c e i v e d i s a l s o performed.  A t every p o i n t o f r e c e p t i o n , d a t a are t e s t e d to ensure t h a t  c o r r e c t or acceptable begin with ETX  and  w i l l be  SOH,  the BCC.  c o n t r o l c h a r a c t e r s are r e c e i v e d .  f o l l o w e d by  the S e l e c t C h a r a c t e r  and  Messages can  STX,  and  only  terminated  by  F a i l u r e to d e t e c t the c o n t r o l c h a r a c t e r s i n c o r r e c t sequence  f l a g g e d as an e r r o r , and  an e r r o r r e c o v e r y  procedure i s c a l l e d i n t o  effect. The  Select Character  o f e r r o r s i n message b l o c k s u c c e s s i v e message b l o c k s If  t h e r e are an odd  a l s o p l a y s an important  transmission.  r o l e i n the  I t d e t e c t s the p r o p e r  r e c e i v e d and p r e v e n t s  number of message d r o p - o u t s ,  detection  sequence o f  the l o s s o f message b l o c k s . the e r r o r i s always  detected.  A "Time-out" c o n d i t i o n i s a l s o imposed on messages.  The  t r a n s m i t t i n g s t a t i o n expects to r e c e i v e the  within a certain period IBM  the acknowledgement of  (10 seconds f o r the PDP-9 and  360/67) a f t e r i t has  received within  transmitted  a message.  acknowledgement  3 seconds f o r  I f no  the  r e p l y whatsoever i s  t h i s p e r i o d , i t i s assumed t h a t the r e c e i v i n g s t a t i o n has  missed the l a s t message c o m p l e t e l y and  re-transmission  i s called into  effect.  T h i s s a f e g u a r d s the b l a n k - o u t of the e n t i r e communication. Finally, correctly, o f the  to ensure t h a t the key  they are always t r a n s m i t t e d  control characters  t e r p r e t a t i o n o f NAK new  c o u l d be  as ACK.  The  i n duplicate.  disastrous.  are  received  Misinterpreting  s t i l l be  detected  reduce the p o s s i b i l i t y To  through the s e l e c t c h a r a c t e r ,  of being  The  transmit  the l a s t message.  station,  the  i s no  way  of d u p l i c a t e c o n t r o l  confronted  w i t h such  recovery  an ACK  was  characters  conditions.  by means o f  transmission  U n t i l i t receives  this  re-transmission negative  i n e r r o r and w i l l  re-  from the r e c e i v i n g  t r a n s m i t t i n g s t a t i o n w i l l not p r o c e e d to the n e x t message.  The  above e r r o r d e t e c t i o n and  t h a t i t cannot d e t e c t  c o r r e c t i o n scheme i s not  a l l e r r o r s , e s p e c i a l l y consecutive,  However, the scheme i s q u i t e s u f f i c i e n t  i s o l a t e d e r r o r s , which o c c u r more f r e q u e n t l y i n c o r p o r a t i o n of the  i s concerned.  extent.  This  m u l t i p l e or  than m u l t i p l e e r r o r s .  bursts  With  o f the l i n k a g e  i s important as f a r as  With the r e d u c t i o n  ideal in  f o r d e t e c t i n g s i n g l e or  above scheme, automatic o p e r a t i o n  i s p o s s i b l e to a g r e a t ciency  use  Though  there  t r a n s m i t t i n g s t a t i o n , on d e t e c t i n g a  acknowledgement, assumes t h a t the l a s t  of e r r o r s .  The  c o r r e c t the e r r o r s d e t e c t e d ,  called into effect.  misin-  t r a n s m i t t i n g s t a t i o n would p r o c e e d to a  to r e c o v e r w i t h o u t human i n t e r v e n t i o n . should  any  A s i m p l e example i s the  message w h i l e the r e c e i v i n g s t a t i o n expects the l a s t message.  c o n d i t i o n can  is  control characters  the  system  transmission  effi-  o f human i n t e r v e n t i o n , the e f f e c t i v e  roughput i s c o n s i d e r a b l y  increased.  12  3.  3.1.1  PROVISIONS MADE FOR THE PDP-9  T h e data-phone h a n d l e r  In p r o v i d i n g system programs f o r h a n d l i n g data communication w i t h i n the PDP-9,.the d a t a l i n k t o the IBM 360/67 i s t r e a t e d as one"of the i n p u t output  d e v i c e s o f the PDP-9.  standard I/O  I/O h a n d l e r  The software  i s made a v a i l a b l e i n the form of a  r o u t i n e o f the PDP-9 Input-Output Programming S y s t e m . 7  macro d e f i n i t i o n s a r e p r o v i d e d and can be c a l l e d from PDP-9 assembly  language programs.  When any o f these macros a r e c a l l e d , the h a n d l e r  v i a a CAL, the a p p r o p r i a t e MTS command i s generated IBM  i s entered  and t r a n s m i t t e d to the  360/67 v i a the l i n k . To the IBM 360/67, the PDP-9 l o o k s l i k e one o f the medium speed  terminals. executed  When a MTS command from'the PDP-9 i s r e c e i v e d the command w i l l be  and the output w i l l be d i r e c t e d back to the PDP-9.  d e a l t w i t h by the message r e c e p t i o n r o u t i n e i n the PDP-9.  T h i s w i l l be  The r o u t i n e  checks f o r e r r o r s and i f any a r e d e t e c t e d , w i l l i n i t i a t e r e q u e s t transmission; otherwise, w i l l be output  first  for re-  the message r e c e i v e d i s assumed to be c o r r e c t and  on one o f the o u t p u t  d e v i c e s o f the PDP-9.  Though t r e a t e d as one o f the I/O d e v i c e s o f the PDP-9, the d a t a link differs slightly i n t e r a c t i v e device.  from the o t h e r h a n d l e r s because the IBM 360/67 i s an Itwill  a command from the PDP-9.  respond i n some f a s h i o n whenever i t r e c e i v e s  There i s thus no d i s t i n c t i o n as to whether a d a t a  t r a n s f e r on the d e v i c e i s i n p u t o r output  alone.  Message t r a n s m i s s i o n from  the PDP-9 i s always accompanied by message r e c e p t i o n . IBM  360/67 i s a t i m e - s h a r i n g  the IBM 360/67 responds.  B e s i d e s , s i n c e the  computer, t h e r e i s no c o n t r o l over  the i n s t a n t  Once t h e h a n d l e r has t r a n s m i t t e d a message, i t has  to w a i t i n a r e c e i v e mode f o r t h e message from the IBM 360/67.  Thus, b o t h  13  i n p u t and o u t p u t o f d a t a have to be h a n d l e d whenever a macro i s c a l l e d . The p r o v i s i o n o f the s o f t w a r e as a s t a n d a r d I/O h a n d l e r does n o t only r e l i e v e the programmer from w r i t i n g h i s own r o u t i n e f o r h a n d l i n g d a t a o v e r the l i n k , i t a l s o ensures PDP-9.  c o m p a t i b i l i t y w i t h the M o n i t o r  transfers  System o f the  I n t h i s way, t h e u n i f i e d way o f h a n d l i n g a l l the I/O d e v i c e s o f the  PDP-9 i s p r e s e r v e d .  Details pertaining  to the h a n d l e r a r e g i v e n i n Appendix  II.  3.1.2  The Macros  Ten d i f f e r e n t macros a r e p r o v i d e d . III.  D e t a i l s a r e g i v e n i n Appendix  The Macros p r o v i d e d a r e by no means s u f f i c i e n t  to a l l MTS commands.  Only  t h e more l i k e l y  used  f o r a one to one c o n v e r s i o n  commands are made a v a i l a b l e .  They i n c l u d e commands f o r s e n d i n g d a t a to the IBM 360/67, s t o r i n g a file,  running  the d a t a i n  the d a t a w i t h a compiled o b j e c t program, and t r a n s m i t t i n g t h e  subsequent o u t p u t back to the PDP-9. To send macros, the macro  a p a r t i c u l a r MTS command o t h e r than those p r o v i d e d by the .LINK can be c a l l e d .  T h i s macro n o t on.1y a l l o w s  make up h i s own commands, i t a l s o a l l o w s the u s e r t o s p e c i f y whether s o u r c e o r b i n a r y , and the p a r t i c u l a r output d e v i c e s  the u s e r to  the d a t a mode, used.  F o r d a t a t r a n s f e r to and from the core o f PDP-9, which i s the most e f f i c i e n t way o f t r a n s f e r r i n g d a t a , the macros  .READ and .WRITE can be used.  No d a t a t r a n s f e r to any p e r i p h e r a l d e v i c e i s made and t h i s s e r v e s to i n c r e a s e the e f f e c t i v e  throughput  rate o f data t r a n s f e r s .  One disadvantage  the volume of d a t a t r a n s f e r r e d i s l i m i t e d by the s i z e o f the c o r e  i s that available.  14  3.1.3  Data Modes  Data t r a n s f e r i n USASCII codes i s the o n l y d a t a mode a v a i l a b l e a t present. data.  B i n a r y d a t a t r a n s f e r i s d e s i r a b l e s i n c e the PDP-9 works w i t h b i n a r y  T h i s would r e q u i r e the i n c o r p o r a t i o n o f t r a n s p a r e n t mode b i n a r y d a t a 3  communication p r o c e d u r e s  .  B e s i d e s , because the PDP-9 has an 1 8 - b i t accumu-  l a t o r whereas the IBM 360/67 uses b y t e s in  the number o f b i t s  procedures  used  (8 b i t s ) ,  a compromise has to be made  f o r each d a t a word to ensure  compatibility.  The  f o r t h i s d a t a t r a n s f e r scheme has n o t been f i x e d y e t , b u t i n c o r p o r -  a t i o n o f the scheme i s to be made. One  d a t a c o n v e r s i o n scheme i s made a v a i l a b l e .  T h i s scheme c o n v e r t s  the 18 b i t s b i n a r y d a t a o f the PDP-9 i n t o s i x d e c i m a l d i g i t s t r a n s m i t t i n g them to the IBM 360/67.  Similarly,  i n USASCII* b e f o r e  f o r data r e c e i v e d , conversion  back to b i n a r y i s made b e f o r e they a r e s t o r e d i n the core of the PDP-9.  The  o n l y r e s t r i c t i o n i s t h a t the d a t a must be p o s i t i v e i n t e g e r s w i t h magnitude 18 less  than 2 Any  .  F u r t h e r d e t a i l s o f the d a t a modes a r e g i v e n i n Appendix IV.  o f t h e above d a t a mode t r a n s f e r s can be made v i a the macro .READ,  .WRITE and .LINK by s p e c i f y i n g o f the c a l l i n g p r o c e d u r e s 3.1.4  the c o r r e s p o n d i n g d a t a mode when c a l l e d .  Details  can be found i n Appendix I I I .  E r r o r d i a g n o s t i c messages  E r r o r d i a g n o s t i c messages a r e p r i n t e d on the PDP-9 t e l e t y p e whenever e r r o r s a r e d e t e c t e d by the e r r o r d e t e c t i o n scheme and automatic  recovery  fails.  E r r o r messages are p r i n t e d i n the form DPERYY (Data-phone e r r o r YY) where YY indicates  the type o f the e r r o r t h a t has caused  a standstill.  Errors of this  * ( 16 i n FORTRAN format  the communication  c a t e g o r y a r e mainly  specification).  to come to  due to the g a r b l i n g o f messages  15  on  the l i n e and hence e r r o r s a r e u s u a l l y  t r a n s i e n t s o n l y , i . e . t h e same e r r o r  may n o t o c c u r a g a i n i f the t r a n s m i s s i o n i s r e p e a t e d . Another s e t o f e r r o r messages, p e r t a i n i n g to the Input-Output gramming System (IOPS) o f the PDP-9, i s a l s o made use o f .  Pro-  This s e t of error  messages i s i n d i c a t i v e o f the programming e r r o r s o f the u s e r , and i s n o t r e l a t e d to e r r o r s encountered A complete l i s t V.  transfer.  o f the e r r o r d i a g n o s t i c messages i s g i v e n i n Appendix  I t i s hoped t h a t these two s e t s o f e r r o r d i a g n o s t i c messages s h o u l d p r o v i d e  sufficient  3.1.5  diagnostic a b i l i t y  f o r u s i n g the d a t a - l i n k .  The h a n d l e r r o u t i n e  A schematic can be d i v i d e d i n t o into The  during data  flow c h a r t o f t h e h a n d l e r r o u t i n e i s g i v e n i n F i g . 4. I t  three s e c t i o n s .  the h a n d l e r and i n i t i a l i z a t i o n second  tion.  The f i r s t  s e c t i o n deals with the entry  f o r the p a r t i c u l a r macro t h a t i s b e i n g  called.  p a r t d e a l s w i t h t h e a c t u a l h a n d l i n g o f d a t a t r a n s m i s s i o n and r e c e p -  The t h i r d p a r t d e a l s w i t h e r r o r d e t e c t i o n .  D e t a i l e d flow c h a r t s f o r the  h a n d l e r a r e g i v e n i n Appendix V I .  3.2 3.2.1  The program "TRSFER" O p e r a t i o n as a t e r m i n a l t e l e t y p e  The program "TRSFER", when o p e r a t e d under "command mode", works e s s e n t i a l l y i n the same way a t e r m i n a l t e l e t y p e does.  Users  from  Outputs a r e p r i n t e d  the keyboard  on the t e l e t y p e .  i n the normal way the MTS o p e r a t e s .  can type i n commands  16  PDP -9 M o n i t o r System >  Other d e v i c e handlers  Data phone handler  PART 1 Macro e n t r y and identification  Data t r a n s m i s s i o n and reception with e r r o r recovery  PART 2  Error  routines  PART 3  Data-phone e r r o r detection routine  HALT  Fig.  4.  ,IOPS E r r o r d e t e c t i o n routine  Return to M o n i t o r  Schematic Flow Chart f o r the Data-Phone H a n d l e r R o u t i n e  17  3.2.2  Data  file  transfers  When o p e r a t e d under " t r a n s f e r mode", the program "TRSFER" can be used  forfile  360/67.  t r a n s f e r s between the I/O d e v i c e s o f the PDP-9 and the IBM  Operation i s e s s e n t i a l l y  s i m i l a r to the P e r i p h e r a l  Program (PIP)'' used under the M o n i t o r System. board, paper  tape r e a d e r and DECtapes.  tape punch o r DECtapes.  Interchange  Input d e v i c e s i n c l u d e key-  Output d e v i c e s can be t e l e t y p e ,  The s t r u c t u r e o f a t y p i c a l  file  paper  t r a n s f e r command i s  * as f o l l o w s : -  T OPDEV : OPFILE «- IPDEV : IPFILE where OPDEV and IPDEV s p e c i f y devices  the o u t p u t and i n p u t respectively.  OPFILE and IPFILE s p e c i f y  the o u t p u t and i n p u t  filenames and EXT i s the f i l e of  ; EXT4-  respectively,  extension specifying  the type  data t r a n s f e r — w h e t h e r source o r b i n a r y .  F o r example, the command T 360 : F I L E 1 + causes to  DTI : FILE2 ; SRC 4-  d a t a s t o r e d i n s o u r c e . f i l e FILE2 on DECtape u n i t 1 to be t r a n s f e r r e d  FILE1 i n IBM 360/67. Filenames  a r e r e q u i r e d o n l y when the d e v i c e i s f i l e - o r i e n t e d .  For  n o n - f i l e - o r i e n t e d d e v i c e s , no f i l e n a m e s p e c i f i c a t i o n i s n e c e s s a r y . A schematic  flow c h a r t f o r t h i s program (TRSFER) i s shown i n F i g . 5.  D e t a i l s o f the o p e r a t i o n procedure  under both  command and t r a n s f e r modes a r e  g i v e n i n Appendix V I I and d e t a i l flow c h a r t s are g i v e n i n Appendix V I I I .  * 4- denotes  c a r r i a g e r e t u r n o r a l t e r n a t e mode  TRSFER  T r a n s f e r mode  Command mode  <  Get  command  Decode command  Send command to 360  F i l e transfer to PDP-9  F i l e transfer to 360  y  Output on t e l e t y p e  Send command to 360  Send d a t a to 360  <  Re t u r n  Store data i n PDP-9  Return  Return  Fig.  5.  Schematic Flow Chart f o r Program "TRSFER"  19  4.  The t h e s i s was  d a t a - l i n k was  written.  The  DISCUSSION  still  not  cause o f i n c o m p l e t i o n  s u p p o r t r o u t i n e i n the PDP-8 a t the operation  o f the l i n k a g e .  i s p o s s i b l e at present. teletype  terminal.  operational.  The  As  f u l l y operational  to the l a c k of a  device  Computing C e n t r e to h a n d l e the i n t e r a c t i v e  Only d a t a t r a n s f e r Command f o r the  f a r as  i s due  at the time when t h i s  from the IBM  t r a n s f e r has  to be  360/67 to the PDP-9 entered  from a  t h i s p a r t i s concerned, the l i n k a g e i s  t e s t s have been c a r r i e d out q u i t e s u c c e s s f u l l y .  now  Slight  communication problems arose when o u t p u t was  made on  i s because the  i t u s u a l l y takes more than 3  t e l e t y p e i s a slow d e v i c e  s e c o n d s — t h e "time-out" p e r i o d — t o transmission  and  complete t y p i n g out  a line.  Very  This  often,  r e c e p t i o n o c c u r at the same time, r e s u l t i n g i n the l o s s o f  •the acknowledgement message. ACK  and  the PDP-9 t e l e t y p e .  T h i s problem has  whenever a message which has  message i s r e c e i v e d .  been c a r r i e d out, no  the same S e l e c t C h a r a c t e r  There i s the  an i r r e c o v e r a b l e e r r o r under any  been overcome by  r i s k of missing  circumstances.  such problem has  as  sending  the l a s t  message b l o c k s , but  an accepted that i s  For a l l the t e s t s t h a t have  occurred.  T r a n s m i s s i o n o f d a t a from the PDP-9 to the computing c e n t r e has been t e s t e d by Centre.  The  s e n d i n g d a t a to the DCT  DCT  2000 l i n e - p r i n t e r i n the  2000 i s an ASCII communication o u t p u t d e v i c e  the same communication p r o c e d u r e as our on  the DCT  2000.  c o r p o r a t i o n o f the For has  to be  Computing  and works w i t h  Data r e c e i v e d a r e  printed  communication problem a r i s e s , e s p e c i a l l y a f t e r the i n -  " t i m e - o u t " scheme i n the PDP-9.  c o m p l e t i o n o f the l i n k a g e ,  tested. The  No  linkage.  also  I t i s hoped t h a t  present  the i n t e r a c t i v e communication scheme  t h i s w i l l be  completed i n the near f u t u r e .  communication system, a f t e r c o m p l e t i o n , s h o u l d  u s e f u l a p p l i c a t i o n s f o r the PDP-9 u s e r s .  More s o p h i s t i c a t e d d a t a  provide  processing  20  problems than b e f o r e still  can be  room f o r improvement.  T h i s w i l l be  a f i r s t step  over the l i n k a g e .  Of  the  transmission  problems at the  A higher  data  to the p r o c e s s  course,  p r i o r i t y o v e r o t h e r I/O ing  c a r r i e d out on  attached  r a t e , although  However, there i s  transmission  rate i s desirable.  o f c a r r y i n g out  t h e r e w i l l s t i l l be  devices  transmission  the PDP-9.  r e a l - t i m e programming  the n e c e s s i t y o f  to the IBM  360/67.  having  Also, i n increas-  the p r e s e n t h a n d l e r works w i t h no  r a t e of 2400 b i t s / s e c . (and s h o u l d s t i l l  p r o p e r l y when the r a t e i s i n c r e a s e d to 4800 b i t s / s e c . which i s l i k e l y e f f e c t i v e soon), time n e c e s s a r y  d e t a i l e d c o n s i d e r a t i o n s have to be  given  to ensure t h a t the program w i l l s t i l l  problems when the  transmission  to the  f e a t u r e s , the l i n k a g e would become a v e r y  system f o r the two  computers.  to be  timing  r a t e i s i n c r e a s e d beyond 4800 b i t s / s e c .  can i n t e r r u p t the d a t a communication at any  o f these  work  execution  execute w i t h o u t  i n c o r p o r a t i o n o f an a t t e n t i o n i n t e r r u p t i s a l s o d e s i r a b l e so users  timing  time.  The  t h a t PDP-9  With the i n c o r p o r a t i o n  u s e f u l communication  21  APPENDIX I :  T a b l e o f USASCII codes f o r i n t e r - c o m p u t e r communications*  First category (standard USASCII definitions) • Control charocters  Third category designated as argument characters (includes the USASCII control charocfer DEL)  Communication control characters Control character DEL included in the argumeijf set Second cotegory designated os Key characters for odditional controls  * This  t a b l e i s taken from Bhushan and S t o t z ' s paper .  22  APPENDIX II:... The Data-Phone  2.1  Handler  General  Communication a CAL i n s t r u c t i o n ,  between the u s e r program and the h a n d l e r i s made v i a  f o l l o w e d by the p e r t i n e n t argument  o f the n o n - r e e n t r a n t  type, which uses  to l e a v e the h a n d l e r a t p r i o r i t y mode and the memory p r o t e c t .  the DBR  list.  (debreak  The h a n d l e r i s  and r e s t o r e ) i n s t r u c t i o n  l e v e l 4, and r e s t o r i n g the l i n k , the extend  The c o n t e n t o f the accumulator  a t the time o f CAL  i s n o t saved.  2.2  I n c o r p o r a t i o n o f the h a n d l e r i n t o  the system  tape  The h a n d l e r i s i n c o r p o r a t e d i n t o the system Details  tape i n the u s u a l way.  can be found i n S e c t i o n 3.4.4.7 (P .3-21) i n the PDP-9 Advanced S o f t -  ware System M o n i t o r s Manual (DEC-9A-MAA0-D).  Information pertaining  to t h i s  h a n d l e r i s as f o l l o w s : a.  The h a n d l e r name i s DPH.  b.  Four s k i p IOTs s h o u l d be i n SKIP CHAIN f o r t h i s d e v i c e h a n d l e r . STF  702521  SKIP ON TRANSMIT FLAG  SRF  702621  SKIP ON RECEIVE  SEF  702541  SKIP ON RECEIVE END  SRI  702561  SKIP ON RING INDICATOR  FLAG FLAG  S i n c e a l l the above IOT s k i p s o c c u r when the f l a g i s NOT s e t , i t i s necessary  to precede  each o f these IOTs by a minus s i g n when e n t e r i n g them i n t o  the SKIP CHAIN. A f t e r the new system has  to be updated  into  tape has been g e n e r a t e d ,  the system  the b i n a r y program  l i b r a r y program (.LIBR).  DPH.  Once t h i s has been  completed, the data-phone h a n d l e r i s then a v a i l a b l e f o r usage. The p r e s e n t working v e r s i o n o f the data-phone h a n d l e r has a memory s i z e o f 3567  Q  o  core l o c a t i o n s .  t a i n e d by d i s p e n s i n g w i t h  A s h o r t e r v e r s i o n o f the h a n d l e r can be ob-  the macros  t h a t a r e n o t b e i n g used.  F o r example,  by d e l e t i n g t h e .SIGON, .SIGOF. and .RUN macros, the h a n d l e r would o n l y r e q u i r e 3335  fi  core  locations.  24  APPENDIX I I I :  Macros; p r o v i d e d f o r  3.1 FORM:  The  macros  u s i n g the l i n k a g e a r e as f o l l o w s :  NAME  FUNCTION CODE  PURPOSE  .INIT  1  Initialize  .SIGON  2  Initiate  communication between PDP9 & 360  .COPY  3  Initiate  .READ macro  .CREAT  4  Initiate  .WRITE macro  .RUN  5  Send a gRUN command to 360  .SIGOF  6  Terminate,  .LINK  7  Send commands as d e s i g n a t e d by  .READ  10  T r a n s f e r d a t a to u s e r l i n e b u f f e r  .WRITE  11  T r a n s f e r d a t a from u s e r l i n e b u f f e r  .WAIT  12  D e t e c t completion o f each command to 360  .TRAN  13  Illegal  the d e v i c e h a n d l e r  communication user  f u n c t i o n code to 360  .INIT .INIT  a,F,R  VARIABLES:  a = D e v i c e Assignment T a b l e (.DAT) s l o t number ( i n o c t a l  radix)  F  (not used) T h e r e f o r e can have e i t h e r the v a l u e 0 o r 1  R  (not used)  EXPANSION:  CAL + F _ g + ?  a _ g  1 7  1 R 400 DESCRIPTION:  The macro .INIT i n i t i a l i z e s the data-phone h a n d l e r . a .SETUP f o r the I0T s k i p  flags.  I t performs  .INIT must be g i v e n p r i o r to  any I/O commands r e f e r e n c i n g .DAT s l o t a; a s e p a r a t e command must be g i v e n f o r each program.  No f i l e  .INIT  .DAT.slot r e f e r e n c e d by the  type s p e c i f i c a t i o n i s n e c e s s a r y f o r t h i s  d e v i c e as i n p u t and output o c c u r s f o r a l l commands.  3.2  FORM:  .SIGON  .SIGON  VARIABLE:  a, D1,N1,D2,N2  a = .DAT s l o t number ( o c t a l r a d i x ) D l .= address o f ID number N l = ID number word count i n o c t a l (=4) D2 = address o f password and o t h e r o p t i m a l N2 = Password  EXPANSION:  c h a r a c t e r count  parameters  (octal)  CAL + a 2 Dl Nl  ,  D2 N2 DESCRIPTION:  The macro .SIGON i n i t i a t e s the IBM 360/67. the command:  communication between the PDP-9 and  On e n c o u n t e r i n g t h i s macro, the h a n d l e r sends  #SIG  to the IBM 360/67.  IDNO  PW = PSWD  From then on,  *  the l i n k a g e i s a c t i v e and  d a t a t r a n s f e r between the two computers can be made. and PSWD a r e assumed to be packed and D2 r e s p e c t i v e l y .  * The u n d e r l i n e d parameters parameter.  i n 5/7 ASCII a t l o c a t i o n s D l  No header i s r e q u i r e d .  PSWD, i t can i n c l u d e parameters  Both IDNO  F o r the parameter  o t h e r than the password  itself  must be r e p l a c e d by the u s e r w i t h the a p p r o p r i a t e  by i n c r e a s i n g 'PSWD  the word count N2.  Thus i f l o c a t i o n D2 c o n t a i n s  T=50' and N2 i s s p e c i f i e d as 11 ( o c t a l ) , then the time  l i m i t parameter  i s also sent.  27  3.3  . C O P Y  FORM:  .COPY  VARIABLE:  ,D,N  a  a = .DAT s l o t number ( o c t a l D = address  o f filename  N = filename EXPANSION:  radix)  f o r .READ  c h a r a c t e r count ( o c t a l )  CAL + a  3 D  N DESCRIPTION:  The .COPY macro i n i t i a t e s D contains  a c t i o n f o r subsequent  .READ macros.  the IBM 360/67 f i l e n a m e which i s to be t r a n s f e r r e d  to the PDP-9 core l o c a t i o n s p e c i f i e d by the ..READ macro. encountering  t h e .READ macro, the command g C O P  i s sent  FILENAME >SYN5  to the IBM 360/67.  . f o r d i r e c t i n g output  3.4  Note t h a t  .CREAT  VARIABLE:  a,D,N  a = .DAT s l o t number ( o c t a l D = address N = filename  EXPANSION:  CAL + a  4 D N  of filename  '>SYN5' i s the d e v i c e name  o f IBM 360/67 to PDP-9.  .CREAT  FORM:  On  radix)  f o r .WRITE  c h a r a c t e r count ( o c t a l )  28  DESCRIPTION:  The .CREAT macro i n i t i a t e s a c t i o n f o r subsequent  .WRITE macros.  D c o n t a i n s the name o f the f i l e , packed i n 5/7 ASCII, which i s to be c r e a t e d i n the 360. On e n c o u n t e r i n g sent.  I t must precede  any .WRITE macros.  t h i s macro, the f o l l o w i n g two commands a r e  , gCRE  FILENAME  gNUM The  u s e r s h o u l d check beforehand  space  3.5  FORM:  t h a t he has s u f f i c i e n t  file  f o r e n t e r i n g u s e r ' s d a t a when the .WRITE macro i s executed.  .RUN  .RUN  VARIABLE:  a,Dl,Nl,D2,N2,D3,N3 a = .DAT s l o t number  D l .= address  (octal radix)  o f the o b j e c t f i l e n a m e i n IBM 360/67 which i s to be  executed N l = Object D2 = address  f i l e f i l e n a m e c h a r a c t e r count  o f the f i l e n a m e where d a t a i s s t o r e d i n IBM 360/67  N2 = Data f i l e f i l e n a m e c h a r a c t e r count D3 = a d d r e s s  (octal)  o f the f i l e  (octal)  name where r e s u l t i s to be s t o r e d i n  IBM 360 N3 = Output f i l e f i l e n a m e c h a r a c t e r count EXPANSION:  CAL + a 5 Dl Nl D2 N2 D3 N3  (octal)  29  DESCRIPTION:  The .RUN macro sends t h e command gRUN OPFILE  to t h e IBM 360/67.  OBFILE  5 = DATAFILE  6 =  The o b j e c t f i l e OBFILE s t o r e d i n  5/7 ASCII a t l o c a t i o n D l i s to be e x e c u t e d .  Data i s obtained  from  DATAFILE which i s s t o r e d a t D2, and r e s u l t s a r e o u t p u t on OPFILE s t o r e d a t D3.  3.6  FORM:  ^  .SIGOF  .SIGOF  VARIABLE:  a  a = .DAT S l o t number  EXPANSION:  (octal  radix)  CAL + a 6  DESCRIPTION:  The .SIGOF macro when c a l l e d sends gSIG  SHORT  command to t h e  IBM 360/67, thus t e r m i n a t i n g the communication between t h e two computers.  F u r t h e r communication i s r e - e s t a b l i s h e d o n l y i f  .SIGON macro i s a g a i n  3.7  FORM:  called.  .LINK  .LINK  VARIABLE:  a,M,D,L,N  a = .DAT s l o t number  (octal  radix)  M = d a t a mode D = output  device  0-KTTA t e l e t y p e 1+DT1 DECtape 1 2+DT2 DECtape 2 3->PP paper punch L = address o f the l i n e b u f f e r where the u s e r ' s command i s s t o r e d  N = number o f c h a r a c t e r s i n the command ( o c t a l ) EXPANSION:  CAL + M _ &  8  +  a g  _  1  7  7 D L N DESCRIPTION:  The .LINK macro when c a l l e d sends the user's to the IBM 360/67 f o r e x e c u t i o n . l o c a t i o n L i n 5/7 ASCII. t e r s i n the command.  ( i n MTS)  The command i s s t o r e d a t  N i s the number  D specifies  command  ( i n o c t a l ) o f charac-  the output  d e v i c e where the  r e s u l t a f t e r the e x e c u t i o n o f the command i s to be t r a n s f e r r e d t o , and M s p e c i f i e s  3.8  FORM:  the data mode (0 = b i n a r y , 2 = 5/7 A S C I I ) .  .READ  .READ a,M,L,W  VARIABLES:  a = .DAT s l o t number M = Data mode  (octal  radix)  0 = binary 1 = image 7 b i t s  ASCII  2 = 5/7 ASCII L = Data b u f f e r  address  W = Data B u f f e r c h a r a c t e r count two word header EXPANSION:  CAL + M, „ + a. . _ o-o y - i /  10 L .DEC  -W  ( d e c i m a l r a d i x ) , i n c l u d i n g the  31  DESCRIPTION:  The .READ macro causes s e n t to IBM 360/67. previous  the command gCOP  The FILENAME•must  .COPY macro.  FILENAME  >'SYN5+to be  be s p e c i f i e d by a  Data i s t r a n s f e r r e d to the d a t a b u f f e r  a r e a a t l o c a t i o n L, and i n the d a t a mode as s p e c i f i e d by M. The number o f words read i n t o L i s d e l i m i t e d by W o r when an EOF i s encountered  as i n d i c a t e d by the IBM 360/67.  o f d a t a i s t e r m i n a t e d by a c a r r i a g e  3.9  FORM:  Each  line  return.  .WRITE  .WRITE  VARIABLES:  a,M,L,W  a = .DAT s l o t number M = D a t a mode  (octal radix)  0 = binary 1 = image 7 b i t s 2=5/7  L = Data b u f f e r  ASCII  ASCII  address  W = Data b u f f e r c h a r a c t e r count  ( d e c i m a l r a d i x ) i n c l u d i n g the  two-word header EXPANSION:  CAL + M, + a_ o—p y—i/ Q  n n  11 L .DEC -W DESCRIPTION:  The .WRITE macro t r a n s f e r s d a t a s p e c i f i e d by L to the IBM 360/67. Data t r a n s f e r s t o p s when the c h a r a c t e r count goes to zero o r when an " a l t e r n a t e mode" i s encountered. a"carriage return". active f i l e ,  Each, l i n e i s t e r m i n a t e d by  The d a t a i s t r a n s f e r r e d to the c u r r e n t l y  and i s n o r m a l l y s p e c i f i e d by the .CREAT macro.  At  32  the end o f d a t a t r a n s f e r , #UNN f o l l o w e d by $ENDFILE commands are sent b e f o r e e x i t  -3.10  FORM:  from t h i s macro.  .WAIT  .WAIT  VARIABLE:  a  a = .DAT s l o t number ( o c t a l  EXPANSION:  radix)  CAL + A 12  DESCRIPTION:  .WAIT macro d e t e c t s the c o m p l e t i o n  o f each macro command. I t  s h o u l d be used a f t e r a l l the data-phone macros w i t h t h e e x c e p t i o n o f .LINK b e f o r e  the l i n e b u f f e r a s s o c i a t e d ' i s used a g a i n , to  ensure the data t r a n s f e r i s complete.  I f .LINK i s used,  3 2 s h o u l d be checked f o r i n p u t - o u t p u t 8  completion.  Q  c o n t a i n s a -1, a l l i n p u t and output and  location  When i t  f o r t h i s macro a r e f i n i s h e d ,  c o n t r o l can then be r e t u r n e d to u s e r ' s program.  33  APPENDIX IV:  4.1  Line Buffer  Data T r a n s m i s s i o n Paths  Headers  L i n e b u f f e r s f o r t h i s h a n d l e r have the same format as those used by the  I/O M o n i t o r System.-. ( S e c t i o n 2.1.1 o f PDP-9 M o n i t o r Manual).  c o m p a t i b i l i t y w i t h the o t h e r I/O d e v i c e s o f the system. are  This  ensures  Two header words  r e s e r v e d f o r each b u f f e r and the a c t u a l d a t a s t a r t s a f t e r header word 1.  Header word 1 i s n o t used by t h i s h a n d l e r . used t o i n d i c a t e the I/O mode.  14-17 a r e  The p o s s i b l e b i t combinations a r e as f o l l o w s : -  0000  =  b i n a r y mode 0  0001  =  Image ASCII mode 1  0010  =  5/7 ASCII mode 2  0101  =  EOF (end o f f i l e ) ,  no o t h e r b i t combinations b e i n g used. count, i n c l u d i n g  F o r header word 0, b i t s  the header word p a i r .  B i t s 1-8 a r e used f o r t h e word p a i r But they o n l y g i v e the c o r r e c t word 8  p a i r count i f the d a t a i n p u t o r output word p a i r count i s l e s s than 2 -1. B i t s 0, and b i t s  4.2 4.2.1  9-13 a r e n o t used.  Data Modes B i n a r y mode 0  In  t h i s mode, d a t a has the form o f 18 b i t s b i n a r y i n the l i n e  Each word i s f i r s t converted i n t o first  c o n v e r t e d to d e c i m a l i n ASCII b e f o r e t r a n s m i s s i o n .  the format 16.  c o n v e r t e d back  buffers.  F o r d a t a coming  It is  from the IBM 360/67, they a r e  to 18 b i t s b i n a r y before, they a r e packed i n t o  A g a i n the format o f the data coming  buffers.  the l i n e  i n i s assumed to be 16.  4.2.2  Image ASCII mode 1  I n t h i s mode, each word i n the b u f f e r i s assumed to be ready i n the form o f 7 b i t s ASCII and i s thus t r a n s m i t t e d d i r e c t l y w i t h o u t c o n v e r s i o n word by word.  4.2.3  Data r e c e i v e d a r e packed  i n a s i m i l a r way.  5/7 ASCII mode 2  D a t a i s assumed to be packed i n the form o f 5/7 ASCII.  They a r e  compatible w i t h t h e IOPS ASCII except t h a t t h e eighth, b i t used d u r i n g d a t a t r a n s f e r i s taken as the odd p a r i t y b i t r a t h e r than even  parity.  35  APPENDIX V:  Error Detection  and H a n d l i n g  Two s e t s o f e r r o r messages a r e i n c o r p o r a t e d The  first  The  second s e t i s p e r t i n e n t  usually  5.1  set, pertaining  indicates  i n the data-phone h a n d l e r .  to the .IOPS, i s u s e f u l f o r debugging programs. to d a t a t r a n s m i s s i o n  irrecoverable  Data-Phone E r r o r Messages  o v e r t h e l i n k a g e and  errors.  (DPER)  E r r o r messages a r e i n the form o f DPERXX where XX i n d i c a t e s the error  code. n o t a c c e p t e d by IBM 360  (1)  DPER00 = Message t r a n s m i t t e d  (2)  DPER01 = Acknowledgement from IBM 360  (3)  DPER02 = Acknowledgement n o t a c c e p t e d by IBM 360  (4)  DPER03 = End o f t r a n s m i s s i o n  (5)  DPER04 = G a r b l e d c o n t r o l c h a r a c t e r s  garbled  not r e c e i v e d by the  360  IBM  r e c e i v e d a t the PDP-9  end (6)  DPER05 = Data s e t n o t ready w h i l e e n t e r i n g  r e c e i v e mode.  (IOPS04 i s i n d i c a t e d i f power i s n o t turned on at the b e g i n n i n g o f t r a n s m i s s i o n ) (7)  DPER06 YY:  Garbled text received the  YY = 01  cause o f t e x t  by the PDP-9.  YY  indicates  garbling.  Wrong s e l e c t c h a r a c t e r s  i . e . an odd number o f  text l i n e s are missed. =02  ->  = 04 =10  No S t a r t o f T e x t  (STX) c h a r a c t e r  Wrong b l o c k c h e c k i n g ->  received  character  Wrong v e r t i c a l p a r i t y d e t e c t e d i n one o r more characters  o f the t e x t  36  = 20 For m u l t i p l e codes. error  5.2  -*• No end o f t e x t c h a r a c t e r e r r o r s , YY w i l l  Thus YY = 14 i n d i c a t e s  received  appear as a combination o f the above  t h a t b o t h v e r t i c a l and l o n g i t u d i n a l p a r i t y  occurred.  .TOPS e r r o r  messages  E r r o r message i s i n the form o f IOPS NN XXXXXX where NN i s the e r r o r code and XXXXXX the a d d i t i o n a l r e l a t e d mation, u s u a l l y  address o f CAL.  (Refer  infor-  to PDP-9 M o n i t o r s Manual S e c t i o n  2.6  for details) . (1)  IOPS04 -  D a t a - s e t n o t ready  (2) IOPS06 - I l l e g a l  function  f o r device handler.  handler, function (3) IOPS07 - I l l e g a l  In this  code 13 ( o c t a l ) i s i l l e g a l  d a t a mode f o r d e v i c e h a n d l e r .  At present,  o n l y mode 0,1,2 a r e l e g a l d a t a modes f o r .READ and .WRITE (4) I0PS11 - .COPY (.CREAT) n o t executed b e f o r e  .READ  (.WRITE)  macro ( 5 ) I0PS16 - Output b u f f e r o v e r f l o w . more c h a r a c t e r s  are received  The above s e t o f e r r o r messages u s u a l l y programmer. o v e r the d a t a  They do n o t i n d i c a t e e r r o r s link.  This  o c c u r s on .READ when than s p e c i f i e d .  indicates  encountered d u r i n g  e r r o r s made by the t r a n s f e r of data  APPENDIX VI  Enter  Handler  Get f u n c t i o n code  Yes I n t e r r u p t Skip  Print Error Return to M o n i t o r  Enter Jump to S e r v i c e  .INIT  Routine  I  Save AC  R e t u r n Standard Buffer size Memory Setup f o r f l a g s  Protect  Yes —«—  C l e a r I/O underway  Service transmit flag Yes  Break from l e v e l 4 Service receive flag R e t u r n to u s e r ' s program  Yes -«— Service end f l a g . Yes Service ring indicator Read s t a t u s  (I)  The H a n d l e r I n i t i a l i z a t i o n  Routines  and h a l t  Chain  38  Initialize  to t r a n s m i t  —^^*Send SOH,  SEL, STX  Send Text  I n i t i a l i z e to re-transmit  Send +Q, ETX, BCC  Wait f o r acknowledgement  Initialize  time out  Yes  —«a—  I n i t i a l i z e to send new t e x t  A l t e r nate s e l e c t c naracter Turn C l o c k o f f  Yes  (II)  Text T r a n s m i s s i o n  Routine  39  Synchronize  Initialize  No Set e r r o r indicator 1  BCC  Select OK?  Yes No  —  Set e r r o r  STX?  indicator  R e t u r n to t r a n s m i t mode  Yes  ETX?  Send i  X  Pack t e x t i n t o user's b u f f e r No  \ Outpu t  Retransmit acknowledgement  to r e c e i v e  Yes  buffer  BCC correct?  No Set e r r o r  indicator Yes No  Endflag  Yes No  Send  Error .Encountered?^  NAK  Enough Trials?  Yes P r i n t e r r o r and h a l t  (III)  Text R e c e p t i o n  Routine  40  No  No Error IQPS 11  Check Data mode  Set i n p u t pack r o u t i n e  Set output unpack r o u t i n e  Send #CRE command  Send gCOPY command 1  Send $NUM command  R e c e i v e t e x t and pack  r  i n t o user's b u f f e r  Send t e x t from u s e r ' s buffer •  No «a—C  Finished?  rYes  Exit  Send #UNN command  Send gENDFILE command  Exit  (IV)  The .WRITE and .READ Macros  >  41  .LINK  .SIGON  Set o u t p u t mode  Send gSIGNON command r  Get  'command'  address  Exit  Get 'command' c h a r a c t e r count  I  .SIGOF  Send command Send gSIGNOFF command  Output d a t a on device selected  Exit  No  (V)  The .LINK, .SIGON,  .SIGOF and .RUN Macros  42  APPENDIX V I I :  7.1  Loading  procedure  The Program TRSFER  and commands  The program TRSFER i s l o a d e d by the L i n k i n g Loader. l o a d e d , the data-phone h a n d l e r punch h a n d l e r  (DPH.), Dectape Handler  (PPA.) and paper tape r e a d e r h a n d l e r  B e f o r e l o a d i n g , the u s e r ' s DTA1  1  DTA2  2  DPH  5  PRA  6  PPA  7  TTA  10  When TRSFER s t a r t s  .DAT s l o t  When i t i s  (DTA.), paper  tape  (PRA.) a r e a l l l o a d e d .  d e v i c e s s h o u l d be a s s i g n e d as f o l l o w s :-  execution, i t p r i n t s  the f o l l o w i n g on t h e t e l e t y p e  360-LINK COMMAND MODE # This i n d i c a t e s  t h a t TRSFER i s ready  typed on the same l i n e o f '#' s i g n .  to a c c e p t command from  The u s e r can now use the keyboard  o r d i n a r y remote t e r m i n a l t e l e t y p e by e n t e r i n g MTS commands. p r i n t e d on t h e t e l e t y p e as w e l l . next  the keyboard  S u c c e s s f u l completion  to be as an  Output i s  and r e a d i n e s s f o r the  command i s a g a i n i n d i c a t e d by the '//' s i g n . To e n t e r f i l e  t r a n s f e r mode, the command TRANSFER f o l l o w e d by a  c a r r i a g e r e t u r n (ALT mode i s i l l e g a l ) s h o u l d be e n t e r e d a t the keyboard. s h o r t form T f o l l o w e d by c a r r i a g e r e t u r n i s a l s o v a l i d . TRANSFER-t-, t h e f o l l o w i n g message i s typed, TRANSFER MODE  The  On d e t e c t i n g T+ o r  A t t h i s p o i n t , the user s h o u l d p r e p a r e which a r e r e q u i r e d to be ready  the i n p u t / o u t p u t d e v i c e s  and then type the d a t a f i l e  transfer  command.  When i n command mode, i f a command b e g i n n i n g w i t h T b u t n o t t e r minated i n one o f the two a l l o w e d is  formats  i s encountered,  the message 'WHAT?'  output on t h e t e l e t y p e and the '#' s i g n i s a g a i n p r i n t e d .  The u s e r  will  then have to r e - t y p e the command. To r e v e r t back to command mode when i n t r a n s f e r mode, t h e command C  o r COMMAND  i s typed.  The messages  COMMAND MODE  it will  a g a i n be p r i n t e d In  to i n d i c a t e  t h a t i t i s ready  t o a c c e p t f u r t h e r commands  T r a n s f e r Mode, the g e n e r a l format o f a command s t r i n g i s as  follows:T DEVI : FILE1 -c- DEV2 : FILE2 ; EXT+ where  T indicates f i l e  transfers  DEVI i s the output  device  DEV2 i s the i n p u t d e v i c e FILE1 i s the o u t p u t  filename  FILE2 i s the i n p u t f i l e n a m e and  EXT i s the f i l e  e x t e n s i o n which can be s o u r c e  (SRC) o r  b i n a r y (BIN) E i t h e r the output o r i n p u t d e v i c e has t o be the IBM 360/67, which i ; d e s i g n a t e d as 360.  I t i s a l s o i l l e g a l to have b o t h DEVI and DEV2 as I/O  d e v i c e s o f the PDP-9. oriented.  Filename  can be o m i t t e d i f the d e v i c e i s n o t f i l e -  PDP-9 f i l e n a m e s a r e l i m i t e d  to s i x c h a r a c t e r s whereas 360 f i l e -  names cannot be l o n g e r than 16 c h a r a c t e r s . d e v i c e names a r e i g n o r e d when  encountered.  Spaces i n between f i l e n a m e s and  7.2  1.  E r r o r Messages  'WHAT?  1  i s p r i n t e d when i n command mode, a command i s encountered which b e g i n s w i t h T b u t i s n o t i n the form T4- o r TRANSFER + .  It is  a l s o p r i n t e d when i n t r a n s f e r mode, the command b e g i n s w i t h C but 2.  i s n o t i n the form C4- o r COMMANDS.  'ILLEGAL COMMAND'  i s p r i n t e d when a t r a n s f e r mode command does n o t conform to the s t a n d a r d  3.  'NO OUTPUT DEVICE UNIT?*  format.  i s p r i n t e d i f no output d e v i c e u n i t i s s p e c i f i e d in  the t r a n s f e r mode command.  4.  'NO OUTPUT FILENAME?' i s p r i n t e d  i f no output f i l e n a m e i s s p e c i f i e d .  5.  'SAME DEVICE FOR INPUT AND OUTPUT'  i s p r i n t e d when b o t h i n p u t device units  6.  'NO INPUT DEVICE UNIT?'  7.  'NO INPUT FILENAME?'  8.  'DATA MODE REQUIRED!'  9.  'ILLEGAL DATA MODE'  i s p r i n t e d i f no i n p u t  i s p r i n t e d i f no i n p u t i s printed  a r e 360. device unit i s s p e c i f i e d .  filename i s s p e c i f i e d .  i f no f i l e  i s p r i n t e d i f the f i l e  and output  extension i s given. extension i s neither  SRC n o r  BIN. 10.  'DEVICE NAME TOO LONG'  11.  'FILE NAME TOO LONG'  i s p r i n t e d i f d e v i c e name i s more than 3  characters  i s p r i n t e d i f f i l e n a m e i s more than the a l l o w e d length.  12.  'ILL DEVICE UNIT'  i s p r i n t e d when the d e v i c e name i s i l l e g a l o r when neither  the i n p u t  names i n c l u d e TTA  o r o u t p u t d e v i c e i s 360.  (TT).  s i g n when i n command mode) w i l l entirely.  device  360, DTI, DT2, PPA (PP) , PRA(PR) and  A f t e r p r i n t i n g the e r r o r message, t h e r i g h t b r a c k e t s i g n  entered  Legal  a g a i n be p r i n t e d .  ( o r the //  The command has to be r e -  APPENDIX V I I I  I n i t i a l i z e I/O d e v i c e s  E n t e r command mode  1 Wait f o r command from TTA  Read i n command and t e s t  Yes  Enter Transfer  mode  No  Print Error  Wait f o r command from TTA  Read i n command and t e s t  Send command to 360 and output on TTA Yes  Print Error Yes  Decode command and complete data t r a n s f e r  (I)  O v e r a l l Flow-Chart  f o r Program TRSFER  46  Get output d e v i c e name and f i l e n a m e  Get i n p u t d e v i c e name and filename  Check e x t e n s i o n -source or binary  Yes  No Set ASCII pack and unpack r o u t i n e s Set b i n a r y pack and unpack r o u t i n e s  No  Print error and r e t u r n  No  Initiate file t r a n s f e r to 360  (II)  Initiate file t r a n s f e r to PDP-9  Decoding f i l e T r a n s f e r Commands  47  I n i t i a l i z e input device  I n i t i a l i z e output device  Seek i n p u t f i l e on d e v i c e  Create output on 360  C r e a t e f i l e on PDP- 9  file  Send command t o 360 f o r data t r a n s f e r  T r a n s f e r d a t a from i n p u t d e v i c e t o PDP-9 c o r e  Receive data from 360  Send d a t a to 360  Store data i n output device  No  Yes I/O T e r m i n a t i o n and return  (III)  F i l e T r a n s f e r t o 360  I/O T e r m i n a t i o n and return  (IV)  F i l e T r a n s f e r t o PDP-9  48  REFERENCES  1.  Proposed USA  S t a n d a r d Data Communication C o n t r o l P r o c e d u r e s f o r the USA  Standard Code f o r I n f o r m a t i o n Exchange,Communication Vol. 2.  12, No.  o f the  ACM.  3, March 1969, p. 166-178.  EIA STANDARD  RS-232-B  I n t e r f a c e between Data P r o c e s s i n g  Terminal  Equipment and Data Communication Equipment, O c t o b e r 1965. 3.  E i s e n b i e s , J . L . , Conventions f o r D i g i t a l Data Communication L i n k D e s i g n . IBM Systems J o u r n a l , V o l . 6, No. 4, 1967, p. 267-302.  4.  DP09A B i t - S y n c h r o n o u s D a t a Communication Channel I n s t r u c t i o n Manual. DEC-09-H8AA-D, D i g i t a l Equipment C o r p o r a t i o n , Maynard, Mass., U.S.A.  5.  Proposed USA  S t a n d a r d C h a r a c t e r S t r u c t u r e and C h a r a c t e r P a r i t y  Sense f o r  S e r i a l - b y - b i t Communication i n the American S t a n d a r d Code f o r I n f o r m a t i o n Interchange.  Communication o f the ACM.  V o l . 8, No. 9, Sept. 1965, p.  553-556. 6.  L y n c h , W.C.,  R e l i a b l e F u l l - D u p l e x F i l e T r a n s m i s s i o n o v e r H a l f Duplex  Telephone L i n e s . 7.  Comm. o f the ACM,  V o l . 11, No. 6, June 1968, p. 407-410.  PDP-9 Advanced Software System M o n i t o r s Manual DEC-9A-MAA0-D, D i g i t a l Equipment C o r p o r a t i o n , Maynard, Mass., U.S.A.  8.  Bhushan, A.K.  and S t o t z , R.H.,  Communications.  P r o c e d u r e s and Standards f o r Inter-Computer  AFIPS Conference P r o c e e d i n g s , SJCC, 1968, V o l . 32, p. 95-104.  

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