STLC5411FN datasheet(18/72 Pages) STMICROELECTRONICS

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GCI MODE

The GCI is a standard interface for the intercon-

nection of dedicated ISDN components in the dif-

ferent equipments of the subscriber loop :

In a Terminal, GCI interlinks the STLC5411, the

ISDN layer 2 (LAPD) controller and the voice/data

processing components as an audio-processor or

a Terminal Adaptor module.

In NT1-2, PABX subscriber line card, or central

office line card (LT), GCI interlinks the UID, the

ISDN Layer 2 (LAPD) controllers and eventually

the backplane where the channels are multi-

plexed.

In NT1, GCI interlinks SID-GCI and STLC5411,

via automode (NT1-auto). In Regenerators, GCI

links both STLC5411 UID in automode (NT-RR-

auto, LT-RR-auto). (See Fig. 4a)

Frame Structure

2B+D data and control interface is transferred in a

time-division multiplexed mode based on 8 kHz

frame structure and assigned to four octets per

frame and direction.(see fig.4b).

The 64 kbit/s channels B1 and B2 are conveyed

in the first two octets; the third octet (M: Monitor)

is used for transferring most of the control and

status registers; the fourth octet (SC: Signalling &

Control) contains the two D channel bits, the four

C/I (command/lndicate) bits controlling the activa-

tion/deactivation procedures, and the E & A bits

which support the handling of the Monitor chan-

nel.

These four octets per frame serving one ISDN

subscribers line form a GCI Channel. One GCI

channel calls for a bit rate of 256 kbit/s.

In NT1-2s or subscriber Line Cards up to 8 GCI

channels may be carried in a frame of a GCI mul-

tiplex. The bit rate of a GCI multiplex may be from

256 kbit/s and up to 3088 kbit/s. Adjacent 4-octet

slots from the frame start are numbered 0 to 7.

The GCI channel takes the number of the slot it

occupies. Spare bits in the frame beyond 256 bits

from the frame start will be ignored by GCI com-

patible devices but may be used for other pur-

poses if required (see Fig.4c). GCI channel num-

ber is selected by biasing pins S0,S1,S2.

Physical Links

Four physical links are used in the GCI.

Transmitted data to the line: Bx

Received data from the line: Br

Data clock: BCLK

Frame Synchronization clock: FSa

GCI is always synchronized by frame and data

clocks derived by any master clock source.

A device used in NT mode can deliver clock

sources able to synchronize GCI, either directly,

or via a local Clock Generator synchronized on

the line by means of the SCLK 15.36 MHz output

clock. Frame clock and data clock could be inde-

pendent of the internal devices clocks. Logical

one on the Br output is the high impedance state

while logical zero is low voltage. For E and A bits,

active state is voltage Low while inactive state is

high impedance state.

NT-RR-AUTO

LT-RR-AUTO

NT1-AUTO

SID-GCI

TERMI NAL

NT1

REPET OR

LINE TERMINATI ON

Figure 4a: GCI configurations of the UID

PRIVATE TERMINAL

OR NT1-2

Figure 4a: GCI configurations of the UID.

STLC5411

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