Le58083
Data Sheet
GCI Format and Command Structure
The GCI interface provides communication of both control and voice data between the GCI highway and subscriber line circuits
over a single pair of pins on the Le58083 Octal SLAC device. A complete GCI frame is sent upstream on the DU pin and received
downstream on the DD pin every 125 µs. Each frame consists of eight 4 byte GCI channels (CHN0 to 7) that contain voice and
control information for eight pairs of channels. A particular channel pair is identified by its position within the frame (see Figure
26). Therefore, a total of 16 voice channels can be uniquely addressed each frame. The overall structure of the GCI frame is
shown in Figure 26.
The 4 byte GCI channel contains the following:
■ 2 bytes; B1 and B2 for voice channels 1 and 2.
■ One Monitor (M) byte for reading/writing control data/coefficients to the Le58083 Octal SLAC device for both
channels.
■ One Signaling and Control (SC) byte containing a 6-bit Command/Indicate (C/I) channel for control information and
a 2-bit field with Monitor Receive and Monitor Transmit (MR, MX) bits for handshaking functions for both channels.
All principal signaling (real-time critical) information is carried on the C/I channel. The Le58083 Octal SLAC device
utilizes the full C/I channel capacity of the GCI channel.
Figure 26. Multiplexed GCI Time Slot Structure
FS
0−3
4−7
8−11
12−15
16−19
20−23
24−27
28−31
CHN0
CHN1
CHN2
CHN3
CHN4
CHN5
CHN6
CHN7
DU, DD
8
8
8
8
B1
0
B2
M
2
SC
1
3
6
1
1
MR
MX
C/I
64
Zarlink Semiconductor Inc.
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