1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 6 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU$!4!G0G0#/-5.)#!4)/./6%2G0G04(%G0G04%,%0(/.%G0G0.%47/2+%.%2!,G0G0$!4!G0G0#/-5.)#!4)/.3).4%2 each individual group is DC-balanced by its last bit (L bit):Bit position Group1 and 2 framing signal with balance b
2、it3-11 BV1 channel (first octet) with balance bit12 and 13 DV-channel bit with balance bit14 and 15 FAauxiliary framing bit or Q bit with balance bit16-24 BV2 channel (first octet) with balance bit25 and 26 DV-channel bit with balance bit27-35 BV1 channel (second octet) with balance bit8 Fascicle VI
3、II.1 - Rec. V.23036 and 37 DV-channel bit with balance bit38-46 BV2 channel (second octet) with balance bit47 and 48 DV channel bit with balance bit5.4.2.2 Master to slaveFrames transmitted by the master contain an echo channel (E bits) used to retransmit the DV bits received from theslaves. The DV-
4、echo channel is used for DV-channel access control. The last bit of the frame (L bit) is used for balancing eachcomplete frame.The bits are grouped as follows:Bit position Group1 and 2 framing signal with balance bit3-10 BV1 channel (first octet)11 E, DV-echo-channel bit12 DV-channel bit13 bit A use
5、d for activation14 FAauxiliary framing bit15 N bit (coded as defined in 6.3)16-23 BV2 channel (first octet)24 E, DV-echo-channel bit25 DV-channel bit26 M, multiframing bit27-34 BV1 channel (second octet)35 E, DV-echo-channel bit36 DV-channel bit37 S, layer 1 multiframe channel bit38-45 BV2 channel (
6、second octet)46 E, DV-echo-channel bit47 DV-channel bit48 frame balance bit5.4.2.3 Relative bit positionsAt the slave mode equipment, timing in the direction to the master mode equipment shall be derived from the framesreceived from the master mode equipment.Fascicle VIII.1 - Rec. V.230 9The first b
7、it of each frame transmitted from a slave equipment towards the master equipment shall be delayed,nominally, by two bit periods with respect to the first bit of the frame received from the master equipment. Figure 3/V.230illustrates the relative bit positions for both transmitted and received frames
8、.5.5 Line codeFor both directions of transmission, pseudo-ternary coding is used with 100% pulse width as shown in Figure4/V.230. Coding is performed in such a way that a binary ONE is represented by no line signal; whereas, a binary ZERO isrepresented by a positive or negative pulse. The first bina
9、ry ZERO following the framing balance bit is of the same polarity asthe framing balance bit. Subsequent binary ZEROs must alternate in polarity. A balance bit is a binary ZERO if the number ofbinary ZEROs following the previous balance bit is odd. A balance bit is a binary ONE if the number of binar
10、y ZEROsfollowing the previous balance bit is even.FIGURE 4/V.230Pseudo-ternary code - example of application5.6 Timing considerationsEquipment may employ one of two timing sources, if available, for transmission of frames across the interface:- timing derived from an internal source or from an exter
11、nal source conveyed to the equipment by other means(e.g. timing derived from the receive line timing by a V-DCE). This is referred to as “master timing mode“.Exactly one equipment on a GDCI bus must operate in this mode.- timing derived from the receive side of the interface (“loopback timing“). Thi
12、s is referred to as “slave timingmode“.6 Interface procedures6.1 DV-channel access procedureThe following procedure allows for a number of slave mode equipments connected in a multipoint configuration togain access to the DV channel in an orderly fashion. The procedure always ensures that, even in c
13、ases where two or moreequipments attempt to access the DV channel simultaneously, one, but only one, of the equipments will be successful incompleting transmission of its information. This procedure relies upon the use of layer 2 frames delimited by flags consistingof the binary pattern “01111110“ a
14、nd the use of zero bit insertion to prevent flag imitation (see Recommendation I.441).The procedure also permits equipment to operate in a point-to-point manner.6.1.1 Interframe (layer 2) time fillWhen a slave mode equipment has no layer 2 frames to transmit, it shall send binary ONEs on the DV chan
15、nel, i.e.,the interframe time fill in the slave-to-master direction shall be all binary ONEs.When a master timing mode equipment has no layer 2 frames to transmit, it shall send binary ONEs or HDLC flagson the DV channel, i.e., the interframe time fill in the master-to-slave direction shall be eithe
16、r all binary ONEs or repetitions ofthe octet “01111110“. When the interframe time fill is HDLC flags, the flag which defines the end of a frame may define thestart of the next frame.6.1.2 D-echo channelThe master timing mode equipment, on receipt of a DV-channel bit, shall reflect the binary value,
17、in the nextavailable DV-echo-channel bit position towards the slave mode equipment.10 Fascicle VIII.1 - Rec. V.2306.1.3 DV-channel monitoringSlave mode equipment, while in the active condition, shall monitor the DV-echo channel, counting the number ofconsecutive binary ONEs. If a ZERO bit is detecte
18、d, the equipment shall restart counting the number of consecutive ONE bits.The current value of the count is called C.Note - C need not be incremented after the value eleven has been reached.6.1.4 Priority mechanismLayer 2 frames are transmitted using one of two priority classes. Priority class 1 fr
19、ames are given priority overpriority class 2 frames. Furthermore, to ensure that within each priority class all competing equipments are given a fair accessto the DV channel, once an equipment has successfully completed the transmission of a frame, it is given a lower level ofpriority within that cl
20、ass. The equipment is given back its normal level within a priority class when all equipments have had anopportunity to transmit information at the normal level within that priority class.The priority class of a particular layer 2 frame may be a characteristic of the equipment which is preset at man
21、ufactureor at installation, or it may be passed down from layer 2 as a parameter of the PH-DATA REQUEST primitive. A dual mode(GDCI/ISDN) terminal may thus use the PH-DATA REQUEST primitive to establish the proper priorities for its operation.The priority mechanism is based on the requirement that s
22、lave mode equipment may start layer 2 frame transmissiononly when C (see 6.1.3) is equal to, or exceeds, the value X1for priority class 1 or is equal to, or exceeds, the value X2forpriority class 2. The value of X1shall be eight for the normal level and nine for the lower level of priority. The valu
23、e of X2shall be ten for the normal level and eleven for the lower level of priority.In a priority class, the value of the normal level of priority is changed into the value of the lower level of priority (i.e.,higher value) when the equipment has successfully transmitted a layer 2 frame of that prio
24、rity class.The value of the lower level of priority is changed back to the value of the normal level of priority when C (see 6.1.3) equals the value of the lower level of priority (i.e., higher value).6.1.5 Collision detectionWhile transmitting information in the DV channel, slave mode equipment sha
25、ll monitor the received DV-echochannel and compare the last transmitted bit with the next available DV-echo bit. If the transmitted bit is the same as thereceived echo, the equipment shall continue its transmission. If, however, the received echo is different from the transmittedbit, the equipment s
26、hall cease transmission immediately and return to the DV-channel monitoring state.6.1.6 Priority systemAnnex B describes an example of how the priority system may be implemented.6.2 Activation/deactivation6.2.1 Definitions6.2.1.1 Slave mode equipment states (normally DTE)6.2.1.1.1 State F1 (inactive
27、): In this inactive state, the equipment is not transmitting. This state is entered upon loss of power.6.2.1.1.2 State F2 (sensing): This state is entered after the equipment has been powered on, but has not determined the type ofsignal (if any) being received.6.2.1.1.3 State F3 (deactivated): This
28、is the deactivated state of the physical protocol. Neither the master nor the slaveequipment is transmitting.6.2.1.1.4 State F4 (awaiting signal): When the equipment is requested to initiate activation by means of an ACTIVATEREQUEST primitive, it transmits a signal (INFO 1) and waits for a response.
29、6.2.1.1.5 State F5 (identifying input): At the first receipt of any signal from the master mode equipment, the slave modeequipment ceases to transmit INFO 1 and awaits identification of signal INFO 2 or INFO 4.Fascicle VIII.1 - Rec. V.230 116.2.1.1.6 State F6 (synchronized): When the equipment recei
30、ves an activation signal (INFO 2) from the master, it respondswith a signal (INFO 3) and waits for normal frames (INFO 4).6.2.1.1.7 State F7 (identifying interface): This is a transition state during entry to normal activation. When this state is entered,a timer (T4) is started, and the appropriate
31、(DTE or DCE) identification character is transmitted on the multiframe Q channel.This state continues until either a V-series identification character is received on the multiframe S channel or T4 times out.6.2.1.1.8 State F8 (lost framing): This is the condition where the equipment has lost frame s
32、ynchronization and is awaiting re-synchronization by receipt of INFO 2 or INFO 4 or deactivation by receipt of INFO 0.6.2.1.1.9 State F9 (activated): This is the normal active state with the protocol activated in both directions. Both the masterand slave mode equipments are transmitting normal frame
33、s.6.2.1.2 Master mode equipment states (normally DCE)6.2.1.2.1 State G1 (deactive): In this deactivated state, the equipment is not transmitting.6.2.1.2.2 State G2 (pending activation): In this partially active state, the master mode equipment sends INFO 2 while waitingfor INFO 3. This state will be
34、 entered after receiving an ACTIVATE REQUEST primitive, or on the receipt of INFO 0 or lostframing while in state G3 or G5. Then the choice to eventually deactivate is up to higher layers within the equipment.6.2.1.2.3 State G3 (identifying interface): This is a transition state during entry to norm
35、al activation. When this state isentered, a timer (T4) is started, and the appropriate (DTE or DCE) identification character is transmitted on the multiframeS channel. This state continues until either a V-series identification (DTE or DCE) is received on the multiframe Q channel orT4 times out.6.2.
36、1.2.4 State G4 (pending deactivation): When the equipment wishes to deactivate, it may wait for a timer to expire beforereturning to the deactivated state.6.2.1.2.5 State G5 (active): This is the normal active state where the master and slave mode equipment are transmitting INFO4 and INFO 3 respecti
37、vely. A deactivation may be initiated by a DEACTIVATE REQUEST primitive, or the equipment mayremain in the active state all the time, under non-fault conditions.6.2.1.3 Activate primitivesThe following primitives should be used between layers 1 and 2 and between layer 1 and the management entity int
38、he activation procedures. For use in state diagrams, etc., abbreviations of the primitive names are also given.PH-ACTIVATE REQUEST (PH-AR)PH-ACTIVATE INDICATION (PH-AI)MPH-ACTIVATE REQUEST (MPH-AR)MPH-ACTIVATE INDICATION (MPH-AI)6.2.1.4 Deactivate primitivesThe following primitives should be used be
39、tween layers 1 and 2 and between layer 1 and the management entity inthe deactivation procedures. For use in state diagrams, etc., abbreviations of the primitive names are also given.MPH-DEACTIVATE REQUEST (MPH-DR)MPH-DEACTIVATE INDICATION (MPH-DI)PH-DEACTIVATE REQUEST (PH-DR)PH-DEACTIVATE INDICATIO
40、N (PH-DI)12 Fascicle VIII.1 - Rec. V.2306.2.1.5 Management primitivesThe following primitives should be used between layer 1 and the management entity. For use in state diagrams, etc.,abbreviations of the primitive names are also given.MPH-ERROR INDICATION (MPH-EI)Message unit contains type of error
41、 or recovery from a previously reported error.MPH-INFORMATION INDICATION (MPH-II)Message unit contains information regarding the physical layer conditions. The provisionally defined parameters are:connected, disconnected, attached DTE, attached DCE, attached TE, and attached NT.Note - Implementation
42、 of primitives in equipment is not for recommendation.6.2.2 SignalsThe identifications of specific signals across the GDCI are given in Table 2/V.230. Also included is the coding forthese signals.TABLE 2/V.230Definition of INFO signals (Note 1)Signals from MASTER TO SLAVE Signals from SLAVE TO MASTE
43、RINFO 0 No signalINFO 2 Frame with all bits of BV, DV and(Note 3) DV-echo channels set to binary ZERO.Bit A set to binary ZERO. N and L bits setaccording to the normal coding rules.INFO 4 Frames with operational data on BV, DVand DV-echo channels. Bit A set to binaryONE.INFO 0 No signalINFO 1 A cont
44、inuous signal with the following(Note 2) pattern: Positive ZERO, negative ZERO,six ONEsNominal bit rate = 192 kbit/sINFO 3 Synchronized frames with operational dataon BV and DV channels.Note 1 - For configurations where the wiring polarity may be reversed (see 4.3) signals may be received with the p
45、olarity of the binaryZEROs inverted. All receivers should be designed to tolerate wiring polarity reversals.Note 2 - Slave mode equipment which does not need the capability to initiate activation of a deactivated V.230 interface need not have thecapability to send INFO 1. In all other respects, this
46、 equipment shall be in accordance with 6.2. It should be noted that in the point-to-multipoint configuration more that one slave mode equipment transmitting simultaneously will produce a bit pattern, as received by themaster mode equipment, different from that described above, e.g., two or more over
47、lapping (asynchronous) instances of INFO 1.Note 3 - During the transmission of INFO 2 or INFO 4, the F bits and the M/bits from the master mode equipment provide the Q-bit patterndesignation as described in 6.3.3.Fascicle VIII.1 - Rec. V.230 136.2.3 Activation/deactivation procedure for slave mode e
48、quipment6.2.3.1 General proceduresAll slave mode equipment conforms to the following procedures (these statements are an aid to understanding; thecomplete procedures are specified in 6.2.3.2):a) Equipment, when first connected, when power is applied, or upon the loss of frame alignment (see 6.3.1.1)
49、shall transmit INFO 0. However, an equipment that is disconnected but powered could be transmitting INFO 1when connected.b) Equipment transmits INFO 3 when frame alignment is established (see 6.3.1.2). However, the satisfactorytransmission of operational data cannot be assured prior to the receipt of INFO 4.c) Equipment shall, when power is removed, initiate the transmission of INFO 0 before frame alignment is lost.6.2.3.2 Specification of the procedureThe procedure for equipment to follow during activation/deactivation is shown in the form of a finite state matrixTable 3/
