Motorola PowerQUICC II MPC8280 Series Reference Manual page 914

SMC in UART Mode
Command
Disables transmission of characters on the transmit channel. If the SMC UART controller receives this
STOP
command while sending a message, it stops sending. The SMC UART controller finishes sending any
TRANSMIT
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.
Enables characters to be sent on the transmit channel. The SMC UART controller expects it after
RESTART
disabling the channel in its SMCMR and after issuing the
TRANSMIT
controller resumes transmission from the current TBPTR in the channel's TxBD table.
Initializes transmit parameters in this serial channel's parameter RAM to their reset state and should only
INIT TX
be issued when the transmitter is disabled. The
PARAMETERS
to reset the transmit and receive parameters.
Table 28-5 describes receive commands issued to the CPCR.
Command Description
Use the
ENTER HUNT CLOSE RXBD
MODE
Forces the SMC to close the current receive BD if it is currently being used and to use the next BD in
CLOSE RXBD
the list for any subsequently received data. If the SMC is not receiving data, no action is taken.
Initializes receive parameters in this serial channel parameter RAM to reset state. Issue it only if the
INIT RX
receiver is disabled.
PARAMETERS
28.3.6 Sending a Break
A break is an all-zeros character without stop bits. It is sent by issuing a
command. After sending any outstanding data, the SMC sends a character of consecutive
zeros, the number of which is the sum of the character length, plus the number of start,
parity, and stop bits. The SMC sends a programmable number of break characters
according to BRKCR and then reverts to idle or sends data if a
before completion. When the break completes, the transmitter sends at least one idle
character before sending any data to guarantee recognition of a valid start bit.
28.3.7 Sending a Preamble
A preamble sequence provides a way to ensure that the line is idle before a new message
transfer begins. The length of the preamble sequence is constructed of consecutive ones that
are one-character long. If the preamble bit in a BD is set, the SMC sends a preamble
sequence before sending that buffer. For 8 data bits, no parity, 1 stop bit, and 1 start bit, a
preamble of 10 ones would be sent before the first character in the buffer. If no preamble
28-14
Freescale Semiconductor, Inc.
Table 28-4. Transmit Commands
Table 28-5. Receive Commands
command instead
ENTER HUNT MODE
INIT TX AND RX PARAMETERS
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Description
command. The SMC UART
STOP TRANSMIT
and
INIT TX RX PARAMETERS
for an SMC UART channel.
resets both receive and transmit parameters.
RESTART TRANSMIT
command can also be used
STOP TRANSMIT
is issued
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