Freescale Semiconductor PowerQUICC MPC885 Reference Manual page 806

Serial Management Controllers (SMCs)
29.3.5 Data Handling Modes: Character- and Message-Oriented
UART mode uses the same data structures as other modes. The structures support multi-buffer operation
and allow break and preamble sequences to be sent. Overrun, parity, 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
simplifies 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.
29.3.6 SMC UART Commands
Table 29-5 describes transmit commands issued to CPCR.
Command
Disables transmission of characters on the transmit channel. If the SMC UART controller receives
STOP TRANSMIT
this command while sending a message, it stops sending. The SMC UART controller finishes
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.
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
INIT TX
only be issued when the transmitter is disabled. The
PARAMETERS
be used to reset the transmit and receive parameters.
Table 29-6 describes receive commands issued to CPCR.
Command Description
Use the
ENTER HUNT
MODE
Forces the SMC to close the current RxBD if it is currently being used and to use the next BD in the
CLOSE RXBD
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
29-12
Table 29-5. Transmit Commands
Table 29-6. Receive Commands
command instead of
CLOSE RXBD
INIT TX AND RX PARAMETERS
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Description
command. The SMC UART
STOP TRANSMIT
INIT TX AND RX PARAMETERS
for an SMC UART channel.
ENTER HUNT MODE
resets both receive and transmit parameters.
command can also
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