MPC8280 datasheet(866/1386 Pages) FREESCALE

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Serial Management Controllers (SMCs)

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

28-12

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.

28.3.5

SMC UART Transmit and Receive Commands

Table 28-4 describes transmit commands issued to the CPCR.

Table 28-5 describes receive commands issued to the CPCR.

28.3.6

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 28-4. 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 28-5. 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.

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