1、D 3404583 0066479 7T2 = COMPLMENTARY COPY k:H N I CAL REPORT ETR 017 December 1992 Source: ETSI TC-TE Reference: TTTE 04-1 1 UDC: 621.395 Key words: Terminal Equipment, DTE, DCE Terminal Equipment (TE); Requirements for the attachment of Data Terminal Equipment comprising CCITT V.series type interfa
2、ces to data circuit-terminating equipment for low and medium data signalling rates ETSI European Telecommunications Standards Institute ETSI Secretariat Postat address: 06921 Sophia Antipolis Cedex - FRANCE Office General technical requirements for equipment connected to an analogue subscriber in th
3、e PSTN (Candidate NET 4)“. IS0 9067 (1 987): “Information processing systems - Data communication - Automatic fault isolation procedures using text loops“. IS0 9543 (1 989): “information processing systems - information exchange between systems - Synchronous transmission signal quality at DTE/DCE in
4、terfaces“. 3 Abbreviations For the purposes of this ETR the following abbreviations apply. CSPDN Circuit Switched Public Data Network CRI Call request with number provided with the identification number CRN Call request with number provided CRS Call request with memory address provided DTE Data Term
5、inal Equipment DCE Data Circuit Terminating Equipment EMC Electromagnetic Compatibility ETR ETSI Technical Report ETC European Telecommunication Standard IC Integrated Circuit I-ETS Interim European Telecommunication Standard 3404583 00bb487 879 Page 11 ETR 017:1992 PSPDN Packet Switched Public Data
6、 Network PSTN Public Switched Telephone Network G STN General Switched Telephone Network 4 General requirements The requirements specified hereafter may apply irrespective of the application of the DTE concerned in one of the possible public networks. 4.1 Safety requirements The DTE shall meet the r
7、equirements of CEPT Recommendation T/CD 04-03 21. NOTE: For an interim period, national safety requirements may still apply. 4.2 Electromagnetic compatibility The requirements concerning Electromagnetic Compatibility (EMC) are currently under discussion by other international bodies. NOTE: For an in
8、terim period, national EMC requirements may still apply. 5 Technical requirements for DTEs intended for connection to DCEs attached to the Public Switched Telephone Network (PSTN) 5.1 Data Circuit-Terminating Equipment (DCE) that may be provided by Administrations for connection to the PSTN The prov
9、ision of certain DCEs and of certain types of networks is entirely a subject of national regulations. Users are referred to existing national or CEPT documentation on the subject. 5.2 The interface The DTE interchange circuits shall meet electrical, functional and operational requirements which are
10、specified in the relevant Recommendations of the CCITT V. series (e.g. CCITT Recommendations V.10 131, V.14 141, V.24 151, V.25 161, V.25 bis 171 and V.28 1811, of CEPT (e.g. T/CD 01-14 911 or IS0 (e.g. IS0 21 10 lo, IS0 7480 11 11). For the definitions of interchange circuits see CCITT Recommendati
11、on V.24 5. The following subclauses attempt to summarise requirements which may otherwise only be found dispersed in the referenced international documentation. 5.2.1 Interchange circuits at the data interface In DCEs, interchange circuits may be provided on a mandatory or an optional basis in accor
12、dance with existing Recommendations published by the CCITT or CEPT. Interchange circuits that are mandatory in certain types of DCEs need not necessarily likewise be provided mandatorily in attached DTEs. Only those circuits necessary to assure satisfactory operation of the application the DTE are i
13、ntended to support the need to be controlled or monitored by the DTE. If, however, an interchange circuit is provided on an optional basis in a given DTE, it shall meet the functional and operational requirements as specified herein. Certain interchange circuits are required to be monitored by the D
14、TE. “Monitoring“ in the context of this ETR implies that the relevant circuit shall not only be terminated by a receiver, but that all signals on this circuit shalt be recognized by the DTE, and subsequent actions shall be taken, as specified herein. The receivers of control circuits directed from t
15、he DCE to the DTE shall not solely be edge-triggered but shall, in addition, recognise changed states on the respective interchange circuit. 3404583 0066488 705 Page 12 ETR 017:1992 Receiver circuits may be provided in the DCE or the DTE for which no generator is provided in the complementary equipm
16、ent. Therefore, where a receiver is not connected to a generator, means should be provided in the equipment (DTE or DCE) where the receiver is located to inhibit or disregard any possible false triggering of the receiver. 5.2.2 Functional and operational requirements for interchange circuits 5.2.2.1
17、 Circuit 102 “signal ground or common return“ This circuit is always essential. If protective ground is provided in the DTE, it should be possible to connect signal ground to protective ground. Whether or not the two may actually be connected with each other may be a subject of national regulations.
18、 Conformance should be checked by inspection. NOTE 1: Pole 1 of the 25-pole interface connector according to IS0 21 1 O 11 01 is assigned for connecting the shields between tandem sections of shielded interface cables. Subject to national regulations, this contact may be connected to protective grou
19、nd (if provided in the DTE), to signal ground, or may remain unconnected. NOTE 2: It is good engineering practice to connect the shield of the interface cable only at one side (DTE or DCE) to pole 1 of the respective interface connector, to prevent ground loops. 5.2.2.2 Circuit 103 “transmitted data
20、“ This circuit is essential for the duplex and half-duplex modes of operation. For simplex operation, this circuit may be omitted if only a receiving mode of operation is intended with the DTE concerned. The OFF condition of circuit 106 “indicates that the DCE is not prepared to accept data signals
21、from the DTE“ (see CCITT Recommendation V.24 i51). Any data that is transmitted to the DCE while 106 is OFF may be lost. Conformance should be checked by inspection. NOTE 1: The data signalling rate on this circuit may be different from the data signalling rate on circuit 1 04 “received data“ for ce
22、rtain applications (“asymmetrical duplex mode of operation“). In some applications, DTEs transmitting and receiving start-stop characters are operated with synchronous DCEs incorporating asynchronous-to-synchronous converters according to CCITT Recommendation V.14 41. In these cases, only character
23、lengths of 8, 9, 10 and 11 bits can be used, and the intracharacter signalling rate on circuit 103 shall not deviate by more than + 1 % or - 2,5 % (for the “normal rate range“) and + 2,3 % or - 2,5 % (for the “extended rate range“) from the nominal value (see also subclause 5.2.2.3 for further detai
24、ls). Conformance should be checked by inspection. NOTE 2: DCEs equipped with an asynchronous (start-stop) to synchronous converter according to CCITT Recommendation V.14 i41 will transmit a “start“ polarity of length M to 2 M + 3 bits (where M is the number of bits per character in the selected form
25、at) as 2 M + 3 bits of “start“ polarity (referred to as “break signal“). If the converter detects more than 2 M + 3 bits all of “start“ polarity, it transmits all these bits s “start“ polarity. The DTE shall transmit on circuit 103 at least 2 M bits of “stop“ polarity after the “start“ polarity brea
26、k signal before sending further data characters. m 3404583 0066489 641 m Page 13 ETR 017:1992 Conformance should be checked by inspection. This circuit may be used to signal a DTE not-ready condition to the associated DCE, where this DCE has an error correcting capability according to CCITT Recommen
27、dation V.42 1121. In this case, a DTE not-ready condition is recognized by the DCE by the reception of a DC3 character on this circuit, and shall be cleared by the reception of a DC1 character as specified in the international alphabet (IA) No. 5. This method is be susceptible to misfunctioning wher
28、e DC1 and DC3 characters can appear within the stream of user data, e. g. at the transfer of binary files. An alternate method of flow control using circuit 133 is therefore specified in CCITT Recommendation V.42 121, paragraph 7.3.1. For requirements concerning the signal quality on this circuit se
29、e Clause 8. 5.2.2.3 Circuit 104 “received data“ This circuit is essential for the duplex and half-duplex modes of operation. For simplex operation, this circuit may be omitted if only a transmitting mode of operation is intended with the DTE concerned. NOTE 1: The data signalling rate on this circui
30、t may be different from the data signalling rate on circuit 1 03 “transmitted data“ for certain applications (“asymmetrical duplex mode of operation“). In some applications, DTEs transmitting and receiving start-stop characters are operated with synchronous DCEs incorporating asynchronous to synchro
31、nous converters according to CCITT Recommendation V.14 141. In these cases, only character lengths of 8, 9, 10 and 11 bits can be used. Furthermore, it should be noted that the length of the stop elements of received characters may be reduced by 12,5 % (in the “normal signalling rate range“) or 25 %
32、 (in the “extended signalling rate range“) of the nominal length, depending on the signalling rate range chosen (these values are theoretical and may be slightly exceeded in practical implementations due to technical constraints). DTEs intended for these applications shall be capable of coping with
33、this condition. The definitions of the signalling rate ranges are contained in CCITT Recommendation V.14 141. NOTE 2: Where the DCE associated with the DTE concerned has an error correcting capability according to CCITT Recommendation V.42 1121, this circuit may be used to signal a DCE not-ready con
34、dition. In this case, the DTE should recognize a DC3 character received on this circuit as a DCE not-ready condition, and the reception of a DC1 character as clearance of this condition. The coding of these characters is in accordance with international alphabet (IA) No. 5. It should be noted that t
35、his method can be susceptible to misfunctioning, where DC1 and DC3 characters can appear within the stream of user data, e. Q. where binary files are transferred. An alternate method of flow control is therefore specified in CCITT Recommendation V.42 121, paragraph 7.3.1. For requirements concerning
36、 the signal quality on this circuit see Clause 8. 5.2.2.4 Circuit 105 “request to send“ This circuit is essential where the DTE is intended to be connected to half-duplex DCEs. If this circuit is provided, it shall not be turned OFF in the transmitting mode of the DTE prior to the trailing edge of t
37、he last transmitted data bit being presented to the DCE on circuit 103 “transmitted data“. Conformance should be checked by inspection. If this circuit is provided for the half-dupiex mode of operation and is turned ON and OFF to turn around the transmitting direction of the data channel, it shall n
38、ot be turned ON prior to circuit 106 “ready for sending“ having gone OFF as a response to circuit 105 previously having been turned OFF. m 3404583 00bb490 3b3 m Page 14 ETR O1 7:1992 Conformance should be checked by inspection. 5.2.2.5 Circuit 106 “ready for sending“ This circuit is essential and sh
39、ould be monitored by the DTE. No data shall be presented to the DCE on circuit 103 “transmitted data“ prior to circuit 106 being ON. Conformance should be checked by inspection. NOTE 1: NOTE 2: NOTE 3: The implementation of an error correcting capability inside the DCE requires that a flow control o
40、f transmitted data be feasible between the DTE and the associated DCE, with the DCE turning circuit 106 ON and OFF. Therefore, an interworking with a DCE where this feature is present and activated may not be possible if circuit 106 is not implemented in the DTE. However, the rules for the flow cont
41、rol have not yet been established in international standardisation. It should be noted that DTEs may not monitor the status of circuit 106 prior to each byte to be sent, but only after blocks of data of variable length. Therefore, a buffer of suitable size should be implemented in the DCE. The size
42、of this buffer is not specified in any international documentation. However, it is assumed that the minimum size should be 8 KBytes which would suffice to buffer the contents of a CRT screen, including control characters, etc . Where a circuit 107 ON to circuit 106 ON time-out function is performed
43、by the DTE, it should be noted that the respective delay may be several seconds with certain types of DCEs. Where the DCE associated with the DTE concerned has an error correcting capability according to CCITT Recommendation V.42 121, this circuit may be used to signal a DCE not-ready condition. In
44、this case, the OFF condition of this circuit indicates a DCE not-ready condition which will be cleared by again turning this circuit ON. An alternate method of flow control using DCl/DC3 characters of international alphabet (IA) No.5 on circuit 104 is specified in CCITT Recommendation V.42 i1 21, pa
45、ragraph 7.3.1. 5.2.2.6 Circuit 107 “data set ready“ This circuit is essential where the DTE is equipped with an automatic answering or calling facility (DEU). Implementers are advised to pay particular attention to paragraph 4.4 of CCITT Recommendation V.24 151. 5.2.2.7 Circuits 10811 “connect data
46、set to line“ and 108/2 “data terminal ready“ One of these circuits shall be provided. If circuit 108/1 is provided for answering controlled by the DTE, and the DTE is not capable of recognizing indication INC (“incoming call“), then also circuit 1 25 shall be provided. NOTE 1 : Once circuit 108/x ha
47、s been turned to the ON condition and data communication has been established, the communication ceases as soon as the respective circuit is turned OFF. If an automatic answering or calling facility is provided, either circuit 108/1 (direct call case) or circuit 108/2 (addressed call case) shall be
48、provided. it shall be ensured that no erroneous lock-up can occur at the connection. If, with circuit 107 being ON, no data transfer is initiated until the expiration of a certain time-out, circuit 108/x shall be turned OFF by the DTE. 3404583 00bb4L 2TT Page 15 ETR 017:1992 This may be accomplished
49、 by the provision of a time-out function in the DTE (“non-activity timer“) with a duration of e. g. less than two minutes, which is started after an incoming call has been detected by the DCE, and the DCE has turned ON circuit 125 “incoming call“. NOTE 2: Conformance should be checked by inspection. 5.2.2.0 Circuit 1 O9 “data channel received line signal detector“ This circuit is essential and should be monitored for applications where at the transmitting side of a connection circuit 105 “request to send“ is turned ON and OFF to control flow of information and/or to turn around t
