Motorola MPC8260 - Manual (Page 590)

20-6 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA
Part IV. Communications Processor Module
handling input data, a terminal driver may wait for an end-of-line character or an idle
timeout rather than be interrupted when each character is received. Conversely, ASCII Þles
can be sent as messages ending with an end-of-line character.
When receiving messages, up to eight control characters can be conÞgured to mark the end
of a message or generate a maskable interrupt without being stored in the buffer. This option
is useful when ßow control characters such as XON or XOFF are needed but are not part
of the received message. See Section 20.9, ÒReceiving Control Characters.Ó
20.6 Error and Status Reporting
Overrun, parity, noise, and framing errors are reported via the BDs and/or error counters in
the UART parameter RAM. Signal status is indicated in the status register; a maskable
interrupt is generated when status changes.
20.7 SCC UART Commands
The transmit commands in Table 20-2 are issued to the CP command register (CPCR).
Table 20-2. 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 Þrst 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
Þnishes 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 modiÞed. 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.