Motorola MPC860 PowerQUICC User Manual page 733

27.5 SCC BISYNC Commands
Transmit and receive commands are issued to the CP command register (CPCR). Transmit
commands are described in Table 27-2.
Command
After hardware or software is reset and the channel is enabled in the GSMR, the channel is in transmit
STOP
enable mode and starts polling the Þrst BD every 64 transmit clocks. This command stops transmission
TRANSMIT
after a maximum of 64 additional bits without waiting for the end of the buffer and the transmit FIFO to
be ßushed. TBPTR is not advanced, no new BD is accessed, and no new buffers are sent for this
channel. SYNCÐSYNC or DLEÐSYNC pairs are sent continually until a
STOP TRANSMIT
After transmission resumes, the EOT sequence should be the Þrst buffer sent to the controller.
Note that the controller remains in transparent or normal mode after it receives a
RESTART TRANSMIT
Stops transmission after the current frame Þnishes sending or immediately if there is no frame being
GRACEFUL
sent. SCCE[GRA] is set once transmission stops. Then BISYNC transmit parameters and TxBDs can
STOP
be modiÞed. The TBPTR points to the next TxBD. Transmission resumes when the R bit of the next BD
TRANSMIT
is set and a
Lets characters be sent on the transmit channel. The BISYNC controller expects it after a
RESTART
or a
TRANSMIT TRANSMIT
STOP TRANSMIT
from the current TBPTR in the channelÕs TxBD table.
Initializes all transmit parameters in the serial channelÕs parameter RAM to their reset state. Issue only
INIT TX
when the transmitter is disabled.
PARAMETERS
Receive commands are described in Table 27-2.
Command
Immediately resets the receive BCS accumulator. It can be used to reset the BCS after recognizing a
RESET BCS
control character, thus signifying that a new block is beginning.
CALCULATION
After hardware or software is reset and the channel is enabled in SCCM, the channel is in receive
ENTER HUNT
enable mode and uses the Þrst BD. This command forces the controller to stop receiving and enter
MODE
hunt mode, during which the controller continually scans the data stream for an SYN1ÐSYN2
sequence as programmed in the DSR. After receiving the command, the current receive buffer is
closed and the BCS is reset. Message reception continues using the next BD.
Used to force the SCC to close the current RxBD if it is in use and to use the next BD for subsequent
CLOSE RXBD
data. If data is not being received, no action is taken.
Initializes receive parameters in this serial channelÕs parameter RAM to reset state. Issue only when
INIT RX
the receiver is disabled. An
PARAMETERS
MOTOROLA
Table 27-2. Transmit Commands
can be used when an EOT sequence should be sent and transmission should stop.
command.
is issued.
RESTART TRANSMIT
GRACEFUL STOP TRANSMIT
is issued and the channel is disabled in its SCCM. The controller resumes transmission
INIT TX AND RX PARAMETERS
Table 27-3. Receive Commands
INIT TX AND RX PARAMETERS
Chapter 27. SCC BISYNC Mode
Part V. The Communications Processor Module
Description
command is issued, after a transmitter error occurs, or after a
resets transmit and receive parameters.
Description
resets transmit and receive parameters.
is issued. A
RESTART TRANSMIT
or
STOP TRANSMIT
STOP
27-5