Freescale Semiconductor MPC8260 - Manual (Page 824)

Serial Management Controllers (SMCs)
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
27-12 Freescale Semiconductor
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.
27.3.5 SMC UART Transmit and Receive Commands
Table 27-4 on page 27-12 describes transmit commands issued to the CPCR.
Table 27-5 describes receive commands issued to the CPCR.
27.3.6 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 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
Table 27-4. 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 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.
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 channel’s TxBD table.
INIT TX
PARAMETERS
Initializes transmit parameters in this serial channel’s 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 27-5. Receive Commands
Command Description
ENTER HUNT
MODE
Use the CLOSE RXBD command instead ENTER HUNT MODE for an SMC UART channel.
CLOSE RXBD Forces the SMC to close the current receive BD 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.