30-12
MPC860 PowerQUICC UserÕs Manual
MOTOROLA
Part V. The Communications Processor Module
and framing errors are reported via the BDs. At its simplest, the SMC UART controller
functions in a character-oriented environment, whereas each character is sent with the
selected stop bits and parity. They are received into separate 1-byte buffers. A maskable
interrupt can be generated when each buffer is received.
Many applications can take advantage of the message-oriented capabilities that the SMC
UART supports through linked buffers for sending or receiving. Data is handled in a
message-oriented environment, so entire messages can be handled instead of individual
characters. A message can span several linked buffers; each one can be sent and received as
a linked list of buffers without core intervention, which simpliÞes programming and saves
processor overhead. In a message-oriented environment, an idle sequence is used as the
message delimiter. The transmitter can generate an idle sequence before starting a new
message and the receiver can close a buffer when an idle sequence is found.
30.3.6 SMC UART Commands
Table 30-5 describes transmit commands issued to the CPCR.
Table 30-6 describes receive commands issued to the CPCR.
30.3.7 Sending a Break
A break is an all-zeros character without stop bits. It is sent by issuing a
STOP
TRANSMIT
command. After sending any outstanding data, the SMC sends a character of consecutive
Table 30-5. Transmit Commands
Command
Description
STOP
TRANSMIT
Disables transmission of characters on the transmit channel. If the SMC UART controller receives this
command while sending a message, it stops sending. The SMC UART controller Þnishes sending any
data that has already been sent to its FIFO and shift register and then stops sending data. The TBPTR is
not advanced when this command is issued. The SMC UART controller sends a programmable number
of break sequences and then sends idles. The number of break sequences, which can be zero, should
be written to the BRKCR before this command is issued to the SMC UART controller.
RESTART
TRANSMIT
Enables characters to be sent on the transmit channel. The SMC UART controller expects it after
disabling the channel in its SMCMR and after issuing the
STOP
TRANSMIT
command. The SMC UART
controller resumes transmission from the current TBPTR in the channelÕs TxBD table.
INIT
TX
PARAMETERS
Initializes transmit parameters in this serial channelÕs parameter RAM to their reset state and should only
be issued when the transmitter is disabled. The
INIT
TX
AND
RX
PARAMETERS
command can also be used
to reset the transmit and receive parameters.
Table 30-6. Receive Commands
Command Description
ENTER
HUNT
MODE
Use the
CLOSE
RXBD
command instead of
ENTER
HUNT
MODE
for an SMC UART channel.
CLOSE
RXBD
Forces the SMC to close the current RxBD if it is currently being used and to use the next BD in
the list for any subsequently received data. If the SMC is not receiving data, no action is taken.
INIT
RX
PARAMETERS
Initializes receive parameters in this serial channel parameter RAM to reset state. Issue it only if
the receiver is disabled.
INIT
TX
AND
RX
PARAMETERS
resets both receive and transmit parameters.
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