MPC8280 datasheet(712/1386 Pages) FREESCALE

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SCC UART Mode

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

21-6

Freescale Semiconductor

21.7

SCC UART Commands

The transmit commands in Table 21-2 are issued to the CP command register (CPCR).

Receive commands are described in Table 21-3.

Table 21-2. Transmit Commands

Command

Description

STOP

TRANSMIT

After a hardware or software reset and a channel is enabled in the GSMR, the transmitter starts polling

the first BD in the TxBD table every 8 Tx clocks. STOP TRANSMIT disables character transmission. If the

SCC receives STOP TRANSMIT as a message is being sent, the message is aborted. The transmitter

finishes sending data transferred to its FIFO and stops. The TBPTR is not advanced. The UART

transmitter sends a programmable break sequence and starts sending idles. The number of break

characters in the sequence (which can be zero) should be written to BRKCR in the parameter RAM

before issuing this command.

GRACEFUL

STOP

TRANSMIT

Used to stop transmitting smoothly. The transmitter stops after the current buffer has been completely

sent or immediately if no buffer is being sent. SCCE[GRA] is set once transmission stops, then the

UART Tx parameters, including the TxBD, can be modified. TBPTR points to the next TxBD in the table.

Transmission begins once the R bit of the next BD is set and a RESTART TRANSMIT command is issued.

RESTART

TRANSMIT

Enables transmission. The controller expects this command after it disables the channel in its PSMR,

after a STOP TRANSMIT command, after a GRACEFUL STOP TRANSMIT command, or after a transmitter error.

Transmission resumes from the current BD.

INIT TX

PARAMETERS

Resets the transmit parameters in the parameter RAM. Issue only when the transmitter is disabled. Note

that INIT TX AND RX PARAMETERS resets both Tx and Rx parameters.

Table 21-3. Receive Commands

Command

Description

ENTER HUNT

MODE

Forces the receiver to close the RxBD in use and enter hunt mode. After a hardware or software reset,

once an SCC is enabled in the GSMR, the receiver is automatically enabled and uses the first BD in the

RxBD table. If a message is in progress, the receiver continues receiving in the next BD. In multidrop

hunt mode, the receiver continually scans the input data stream for the address character. When it is

not in multidrop mode, it waits for the idle sequence (one character of idle). Data present in the Rx FIFO

is not lost when this command is executed.

CLOSE RXBD

Forces the SCC to close the RxBD in use and use the next BD for subsequent received data. If the SCC

is not in the process of receiving data, no action is taken.

Note that in an SCC UART controller, CLOSE RXBD functions like ENTER HUNT MODE but does not need to

receive an idle character to continue receiving.

INIT RX

PARAMETERS

Resets the receive parameters in the parameter RAM. Should be issued when the receiver is disabled.

Note that INIT TX AND RX PARAMETERS resets both Tx and Rx parameters.

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