1、INTERNATIONAL TELECOMMUNICATION UNION ITU=T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU SERIES V: DATA COMMUNICATION OVER THE TELEPHONE NETWORK Interfaces and voiceband modems V.80 (08196) In-band DCE control and synchronous data modes for asynchronous DTE ITU-T Recommendation V.80 (Previously ”
2、CCITT Recommendation”) ITU-T V-SERIES RECOMMENDATIONS DATA COMMUNICATION OVER THE TELEPHONE NETWORK 1 - General I .2 e+ *.*. icebed modems 3 - Wide-bandmodems 4 - Errorcontrol 5 - Transmission quality and maintenance 6 - Intenvorking with other networks For further details, please refer to ITU-T Lis
3、t of Recommendations. . STD-ITU-T RECMN V-BO-ENGL 177b 48b259L Ob24432 T4b FOREWORD The ITU-T (Telecommunication Standardization Sector) is a permanent organ of the International Telecommunication Union (ITU). The ITU-T is responsible for studying technical, operating and tariff questions and issuin
4、g Recommen- dations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on t
5、hese topics. The approval of Recommendations by the Members of the IT-T is covered by the procedure laid down in WTSC Resolution No. 1 (Helsinki, March 1-12, 1993). ITU-T Recommendation V.80 was prepared by ITLJ-T Study Group 14 (1993-1996) and was approved under the WTSC Resolution No. 1 procedure
6、on the 16th of August 1996. NOTE 1. telecommunication administration and a recognized operating agency. In this Recommendation, the expression “Administration” is used for conciseness to indicate both a 2. follows: The status of annexes and appendices attached to the Series V Recommendations should
7、be interpreted as - - an annex to a Recommendation forms an integral part of the Recommendation; an appendix to a Recommendation does not form part of the Recommendation and only provides some complementary explanation or information specific to that Recommendation. 0 ITLJ 1997 All rights reserved.
8、No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the IT. Recommendation V.80 (08/96) 1 STD-ITU-T RECMN V-BO-ENGL L77b = LiBb257L 0b2LiLi33 782 1 2 3 4 5 . 6 . 7 8
9、CONTENTS Scope References Definitions Physical layer . Necessary serial interface circuits . 4.2 Represented circuits 4.1 Serial port considerations . 5.1 Serial port rate 5.2 5.3 Flow control interactions . : 5.4 Data stream errors . In-band control procedures 6.1 Basic mode transparency . . Serial
10、 port rate when used in command state 6.2 In-band command execution . 6.3 DTE-to-DCE data streams 6.4 DCE-to-DTE data streams 7-bit in-band command definitions 7.1 V.24 status reporting . 7.2 In-band commands sent by the DTE to DCE 7.3 In-band commands sent by the DCE to DTE 7.4 Extended in-band com
11、mands sent from DTE to DCE 7.5 Extended in-band commands sent from DCE to DTE 7.6 in-band service control . 7.7 Overall service control 7.8 Individual status control . 7.9 7.10 In-band MARK Idle Reporting Control, +IBM %bit commands: Synchronous data modes 8.1 Synchronous modes enable . 8.2 Synchron
12、ous access mode configuration 8.3 Synchronous Mode Indication 8.4 Transmit Flow Control Thresholds . 8.5 Synchronous Access Mode In-Band Commands and Indications 8.6 Synchronous Mode Operation 8.7 Frame Tunnelling Mode Operation 8.8 8.9 Examples . V.25 ter formatted syntax for control of in-band Con
13、trol, +IBC Synchronous Access Mode Operation Appendix I . Configuring the DTE-DCE Interface in Synchronous Access Mode for Multimedia Applications . 1.1 1.2 Minimum DTE-DCE data signalling rate . Flow control thresholds and buffer contents reporting . 11 Recommendation V.80 (08196) Page 1 2 2 3 4 4
14、4 4 4 5 5 5 5 6 7 7 7 7 8 9 10 11 13 14 14 14 16 17 18 20 22 22 23 25 25 25 30 31 31 31 Recommendation V.80 IN-BAND DCE CONTROL AND SYNCHRONOUS DATA MODES FOR ASYNCHRONOUS DTE (Geneva, 1996) 1 Scope Recommendations exist for DTE Control of DCE using serial data interchange and start-stop fiaming (Re
15、comendations V.25 bis, V.25 ter). When user data is not being transferred, DTE commands and DCE responses are delivered on the same data paths used for user data, such as V.24 circuits 103 and 104. The above mentioned Recommendations use out-of-band mechanisms for control while user data is being tr
16、ansferred, such as V.24 circuits 108/2 and 109 for call control and status, and circuits 133 and 106 for flow control. All commands or status messages delivered on circuits 103 and 104 must be applied while user data transfer is suspended or terminated. In addition, Recommendation V.25 ter defines t
17、wo modes of DCE operation while in Online Data State for use with DTE employing asynchronous, start-stop framing; namely, Direct Mode and Buffered Mode. In addition, Recommendations V.42 and V.42 bis define additions to Buffered Mode for error controlled and data compressed operation, respectively.
18、This Recommendation is comprised of 6 elements: 0 It describes procedures for an asynchronous DTE and a DCE to exchange the state of V.24 circuits, whether or not leads for those circuits exist on the V.24 interface, by the use of in-band messages on circuits 103 and 104. A complete set of V.24 circ
19、uit leads are not available on all DTE, due to interface restrictions or DTE system software. 0 It describes time-invariant procedures for an asynchronous DTE and a DCE to exchange sequences of continuous mark or space of extended length, by the use of in-band messages on circuits 103 and 104. Not a
20、ll DTE are capable of generating and/or interpreting such sequences directly. 0 It describes procedures for an asynchronous DTE and a DCE to exchange ordinary V.25 ler commands and indications while in Online Data State, by encapsulating such commands and indications within in-band messages on circu
21、its 103 and 104. 0 It describes procedures for an asynchronous DTE and a DCE to exchange commands and indications for signal converter control and hookswitch status while in Online Data State, by encapsulating such commands and indications within in-band messages on circuits 103 and 104. 0 It descri
22、bes procedures for a Frame Tunnelling Mode of DCE operation during Online Data State, whereby the DCE converts between asynchronous HDLC framing used by a local DTE employing start-stop framing, and synchronous HDLC framing used by the remote data station. 0 It describes procedures for a Synchronous
23、 Access Mode of DCE operation during Online Data State, whereby an asynchronous DTE using start-stop framing can transmit and receive arbitrarily-formatted synchronous bitstreams on the GSTN. These procedures depend on the integrity of the data transfer path. It is preferred that the DTE-DCE link pr
24、ovide some means to prevent loss-of-data errors or other corruption of In-Band control information, or that the expected integrity of the link be such that this is deemed unnecessary. The specification of means to prevent loss-of-data is beyond the scope of this Recommendation. These procedures must
25、 be time-independent because inter-character delay time cannot be preserved in DTE containing multi-tasking software, large character buffers or intermediate data links (eg. Local Area Networks). Recommendation V.80 (08/96) 1 - STD-ITU-T RECMN V-BO-ENGL 179b = 48b257L Ob24435 755 2 References The fo
26、llowing Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; all users of this Reco
27、mmendation are therefore encouraged to investigate the possibility of applying the most recent editions of the Recommendations and other references listed below. A list of currently valid ITU-T Recommendations is regularly published. - ITiJ-T Recommendation T.3 1 (1999, Asynchronous facsimile DCE co
28、ntrol - Service class 1. - ITiJ-T Recommendation T.32 (1995), Asynchronous facsimile DCE control - Service class 2. - CCITT Recommendation V.4 (1988), General structure of signals of International Alphabet No. 5 code for character oriented data transmission over public telephone networks. - ITU-T Re
29、commendation V.24 (1993), List of definitions for interchange circuits between Data Terminal Equipment PTE) and data circuit-terminating equipment (DC). - CCITT Recommendation V.25 bis (1988), Automatic calling and/or answering equipment on the General Switched Telephone Network (GSnV) using the 100
30、-series interchange circuits. - ITU-T Recommendation V.25 ter (1995), Serial asynchronous automatic dialling and confrol. - IS0 21 11 :1985, Datu communication - Basic mode control procedures - Code independent information transfer. - CCITT Recommendation T.50 (1 992), International Reference Alphab
31、et (IRA) formerly International Alphabet No. 5 or IA5), Information technology - 7-bit coded character set for information interchange. - ISOAEC 3309:1993, Information technology - Telecommunications and information exchange between systems - High-level data link control (HDLC) procedures - Frame st
32、ructure. 3 Definitions For the purposes of this Recommendation, the following definitions and abbreviations apply. 3.1 command state: In Command State, the DCE is not communicating with a remote station, and the DCE is ready to accept commands. Data signals from the DTE on circuit 103 are treated as
33、 commands and processed by the DCE, and DCE responses are sent to the DTE on circuit 104. The DCE enters this state upon power-up, and when a call is disconnected. 3.2 online command state: In Online Command State, the DCE is communicating with a remote station, but treats signals fiom the DTE on ci
34、rcuit 103 as commands and sends responses to the DTE on circuit 104. Depending on the implementation, data received from the remote station during OnLine Command State may be either discarded or retained in the DCE until Online Data State is once again entered (from a DTE command). Data previously t
35、ransmitted by the local DTE and buffered by the DCE may be transmitted from the buffer to the remote DCE during Online Command State, or it may be discarded or transmission deferred until Online Data State is once again entered. Online Command State may be entered from Online Data state by a mechani
36、sm defined in Recommendation V.25 ler, or a mechanism defined in this Recommendation, or by other manufacturer-defined means. 3.3 online data state: In Online Data State, the DCE is communicating with a remote station. Data signals from the DTE circuit 103 are treated as data and transmitted to the
37、remote station, and data signals received from the remote station are delivered to the DTE on circuit 104. Data and Control signals are monitored by the DCE to detect events such as loss of the remote station connection and DTE requests for disconnection or switching to Online Command State. Online
38、Data State is entered by successful completion of a command to originate or answer a call, by automatically answering a call, or by DTE command to return to Online Data state from Online Command state. 2 Recommendation V.80 (08196) 3.4 in-band command: An In-Band Command is a two or multiple charact
39、er sequence, consisting of a data link escape Character followed by a command character. If the command character is followed by additional characters as defined in the command definition, this is an extended command; otherwise, it is a short command. Except for the escape character, all short or ex
40、tended command characters are limited to the range of 20h to 7Eh and AOh to FEh. 3.5 in-band control circuit: An In-Band Control Circuit is a logical V.24 circuit defined between DTE and DCE, but which is presented by one device to the other by means of In-Band Commands instead of (or in addition to
41、) by means of physical out-of-band circuits. 3.6 hexadecimal coding: In this Recommendation, hexadecimal coding is used. Hexadecimal is base-16, with the first six letters of the Roman alphabet (A-F) used to represent the digit values 10-15, in addition to the numerals 0-9 used for their traditional
42、 digit values. A single hexadecimal digit represents a four-bit binary number; two consecutive hexadecimal digits represent an 8-bit number, with the first digit representing the 4 most significant bits, and the second digit representing the 4 least significant bits. in this Recommendation, two hexa
43、decimal digits are followed by the lower case “h” to indicated hexadecimal notation. For example, 5Dh represents O101 1101 in binary, or 93 in decimal, or 5/13 in-T.50 character notation. 3.7 circuit 104. break: In this Recommendation, Break refers to extended periods of constant logic-zero on V.24
44、circuit 103 or 1 3.8 circuit 103 or circuit 104. mark idle: In this Recommendation, Mark Idle refers to extended periods of constant logic-one on V.24 3.9 synchronous mode: Mode of data transmission whereby the V.24 circuits 103 (TD) and 104 (RD) transfer data synchronously at the modem-to-line inte
45、rface rate, using V.24 circuits 113 or 114 for transmitter bit timing, and circuit 115 for receiver bit timing. The modem does not buffer data in either direction, nor does it implement flow control. 3.10 frame tunnelling mode: Mode of data transmission whereby the V.24 circuits 103 (TD) and 104 (RD
46、) transfer HDLC fiame data asynchronously, using the stadstop transparency procedures specified in ISOAEC 3309. Data transmission between DCEs uses the synchronous transmission procedures specified in ISOfiEC 3309. in each direction, the DCE converts the HDLC frames between the two formats. This mod
47、e allows existing DTEs using stadstop transparency (e.g. Recommendation T. 123), to take advantage of the higher throughput afforded by synchronous transmission. 3.11 synchronous access mode: Mode of data transmission whereby start-stop framed data octets from V.24 circuit 103 are stripped of the st
48、art and stop bits and concatenated for transmission to the remote DCE. The synchronous bitstream from the remote DCE is divided into octets and transmitted to the local DTE on V.24 circuit 104 with start and stop bits inserted. Flow control is available to allow the DTE-DCE octet transfer rate to be
49、 matched to that of the line without buffer underrun or overrun. While in this mode, operation may be alternated between a Transparent sub-Mode where no additional bit processing is done by the DCE, and Framed sub-Mode where bit-oriented synchronous protocol framing is performed by the DCE. 3.12 transparent sub-mode: Generic Synchronous Access Mode for unspecified DCE-DCE protocols. The transmitted bitstream is as specified by the DE, using the EM-shielding procedures specified here. All received bits are delivered to the DTE, including constant mark idle (ones). 3.13 framed su
