Motorola PowerQUICC II MPC8280 Series Reference Manual page 934

Freescale Semiconductor, Inc.
The SMC in GCI Mode
28.5.2.1 SMC GCI Monitor Channel Transmission Process
Monitor channel 0 is used to exchange data with a layer 1 device (reading and writing
internal registers and transferring of the S and Q bits). Monitor channel 1 is used for
programming and controlling voice/data modules such as CODECs. The core writes the
byte into the TxBD. The SMC sends the data on the monitor channel and handles the A and
E control bits according to the GCI monitor channel protocol. The command
TIMEOUT
resolves deadlocks when errors in the A and E bit states occur on the data line.
28.5.2.2 SMC GCI Monitor Channel Reception Process
The SMC receives data and handles the A and E control bits according to the GCI monitor
channel protocol. When the CP stores a received data byte in the SMC RxBD, a maskable
interrupt is generated. A command causes the MPC8280 to
TRANSMIT ABORT REQUEST
send an abort request on the E bit.
28.5.3 Handling the GCI C/I Channel
The C/I channel is used to control the layer 1 device. The 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).
28.5.3.1 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.
28.5.3.2 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.
28-34 MPC8280 PowerQUICC II Family Reference Manual MOTOROLA
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