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30.5.3 Handling the GCI C/I Channel
The C/I channel is used to control the OSI layer 1 device. The OSI layer 2 device in the TE
sends commands and receives indication to or from the upstream layer 1 device through C/I
channel 0. In the SCIT configuration, C/I channel 1 is used to convey real-time status
information between the layer 2 device and nonlayer 1 peripheral devices (CODECs).
30.5.3.1 SMC GCI C/I Channel Transmission Process
The core writes the data byte into the C/I TxBD and the SMC transmits the data
continuously on the C/I channel to the physical layer device.
30.5.3.2 SMC GCI C/I Channel Reception Process
The SMC receiver continuously monitors the C/I channel. When it recognizes a change in
the data and this value is received in two successive frames, it is interpreted as valid data.
This is called the double last-look method. The CP stores the received data byte in the C/I
RxBD and a maskable interrupt is generated. If the SMC is configured to support SCIT
channel 1, the double last-look method is not used.
30.5.4 SMC GCI Commands
The commands in Table 30-18 are issued to the CPCR.
Command
Initializes transmit and receive parameters in the parameter RAM to their reset state.
INIT TX AND RX
PARAMETERS
This receiver command can be issued when the MPC850 implements the monitor channel
TRANSMIT
protocol. When it is issued, the MPC850 sends an abort request on the A bit.
ABORT
REQUEST
This transmitter command can be issued when the MPC850 implements the monitor channel
TIMEOUT
protocol. It is usually issued because the device is not responding or A bit errors are detected. The
MPC850 sends an abort request on the E bit at the time this command is issued.
30.5.5 SMC GCI Monitor Channel RxBD
The GCI monitor channel RxBD, shown in Figure 30-16, is used by the CP to report on the
monitor channel receive byte. The RxBD itself receives the monitor data.
0
1
Offset + 0
E
L
Figure 30-16. SMC GCI Monitor Channel RxBD
Table 30-18. SMC GCI Commands
2
3
4
5
ER
MS
—
Chapter 30. Serial Management Controllers (SMCs)
Description
6
7
8
9
10
SMC in GCI Mode
11
12
13
14
Data
15
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