Error And Status Reporting; Scc Uart Commands - Freescale Semiconductor MPC850 User Manual

Error and Status Reporting

22.6 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.

22.7 SCC UART Commands

The transmit commands in Table 22-2 are issued to the CP command register (CPCR).
Command
After a hardware or software reset and a channel is enabled in the GSMR, the transmitter starts polling
STOP
the first BD in the TxBD table every 8 Tx clocks.
TRANSMIT
SCC receives
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.
Used to stop transmitting smoothly. The transmitter stops after the current buffer has been completely
GRACEFUL
sent or immediately if no buffer is being sent. SCCE[GRA] is set once transmission stops, then the
STOP
UART Tx parameters, including the TxBD, can be modified. TBPTR points to the next TxBD in the
TRANSMIT
table. Transmission begins once the R bit of the next BD is set and a
issued.
Enables transmission. The controller expects this command after it disables the channel in its PSMR,
RESTART
after a
TRANSMIT STOP TRANSMIT
error. Transmission resumes from the current BD.
Resets the transmit parameters in the parameter RAM. Issue only when the transmitter is disabled.
INIT TX
Note that
PARAMETERS INIT TX AND RX PARAMETERS
Receive commands are described in Table 22-3.
Command
Forces the receiver to close the RxBD in use and enter hunt mode. After a hardware or software reset,
ENTER HUNT
once an SCC is enabled in the GSMR, the receiver is automatically enabled and uses the first BD in the
MODE
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.
Forces the SCC to close the RxBD in use and use the next BD for subsequent received data. If the
CLOSE RXBD
SCC is not in the process of receiving data, no action is taken.
Note that in an SCC UART controller,
receive an idle character to continue receiving.
Resets the receive parameters in the parameter RAM. Should be issued when the receiver is disabled.
INIT RX
Note that
PARAMETERS INIT TX AND RX PARAMETERS
Table 22-2. Transmit Commands
as a message is being sent, the message is aborted. The transmitter
STOP TRANSMIT
command, after a
resets both Tx and Rx parameters.
Table 22-3. Receive Commands
CLOSE RXBD
resets both Tx and Rx parameters.
MPC850 Family User's Manual
Description
disables character transmission. If the
STOP TRANSMIT
command, or after a transmitter
GRACEFUL STOP TRANSMIT
Description
functions like
ENTER HUNT MODE
command is
RESTART TRANSMIT
but does not need to