2629 NTERNATIONAL STANDARD TSO INTERNATIONAL ORGANIZATION FOR STANDARDIZATION·MEKYHAPOIHAOPTAHM3ALMI HO CTAHAAPTH3ALIHH.ORGANISATION INTERNATIONALE DE NORMALISATION Basic mode control procedures -- Conversational information message transfer First edition - 1973-02-15 ISO 2629-1973 (E) Ref. No. ISO 2629-1973 (E) UDC 681.14 Descriptors:dataprocessing,datatransmission,controlprocedures. Price based on 2 pages FOREWORD ISO (the International Organization for Standardization) is a worldwide federation of national standards institutes (IsO Member Bodies). The work of developing International Standards is carried out through ISO Technical Committees. Every Member Body interested in a subject for which a Technical Committee has been set up has the right to be represented on that Committee. International organizations, Draft International Standards adopted by the Technical Committees are circulated to the Member Bodies for approval before their acceptance as International Standards by the Iso Councit. Standard IsO 2629 was drawn up by Technical Committee International ISO/TC 97, Computers and information processing. It was approved in September 1972 by the Member Bodies of the following countries : Germany Australia South Africa, Rep. of Beigium Ireland Spain Brazil Sweden Italy Canada Japan Switzerland Czechoslovakia Thailand Netherlands Denmark New Zealand United Kingdom Egypt, Arab Rep. of Portugal U.S.A. France U.S.S.R. Romania No Member Body expressed disapproval of the document. @ Intemational Organization for Standardization, 1973 : Printed in Switzerland ISO 2629-1973 (E) INTERNATIONAL STANDARD Basic mode control procedures -- Conversational information message transfer 2 REFERENCE 0 INTRODUCTION This Internationat Standard defines an addition to the basic ISO/R 1745, Basic mode control procedures for data mode control procedures for data communication systems communication systems. and allows the reversal of information transfer while remaining in Phase 3 (information transfer) of the basic mode. Aithough applicable to many types of terminals, this type of operation is particularly adaptable to inquiry/response systems. 3 CONVERSATION RULES (See Figure) In some systems, the security of the data link operation may be obtained by the use of block checking and ACK-NAK supervisory sequences. 3.1 The positive acknowledgement can be replaced by the transfer of an information message in the opposite To preserve a high degree of security, it is recognized that direction. numbering schemes (forward and/or backward) can also be used, 3.2 The information message can be sent in lieu of the In other systems utilizing less sophisticated terminals, positive acknowledgement only when the received message supervisory information and control information may be is terminated by ETX (or DLE.ETX); not ETB (DLE.ETB). contained within the message and/or handled by operator These systems are not covered by this procedures. 3.3 The opening character of the returned message (i.e. International Standard. STX, SOH or DLE.STX, DLE.SOH) shall be considered as having the additional meaning of positive acknowledge- ment. 1 SCOPE AND FIELD OF APPLICATION 3.4 If there is no information message to be transferred in the opposite direction after the received message is correctly received, the positive acknowledgement shall be 1.1 This Internationai Standard defines the means by used (see Note 2). the basic mode control procedures defined in ISO/R 1745 3.5 An information message shall never be sent instead of interchange information messages can in fast conversational manner and where the operator plays a a negative acknowledgement, except as indicated in Note 2. significant role in the operation of the terminal. 3.6 Termination is initiated by the station with link 1.2 This International Standard extends Phase 3 responsibility. (information transfer) as defined in ISO/R 1745, to allow two stations connected by a data link to reverse their master/slave status,