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Part IV. Communications Processor Module
Table 23-4 describes receive commands.
Command
After hardware or software is reset and the channel is enabled, the channel is in receive enable mode
ENTER HUNT
and uses the Þrst BD in the table.
MODE
frame and enter hunt mode where the transparent controller waits for the synchronization sequence.
After receiving the command, the current buffer is closed. Further data reception uses the next BD.
Forces the SCC to close the RxBD if it is being used and to use the next BD for any subsequently
CLOSE RXBD
received data. If the SCC is not receiving data, no action is taken by this command.
Initializes all receive parameters in this serial channel parameter RAM to reset state. Issue only when
INIT RX
the receiver is disabled.
PARAMETERS
23.8 Handling Errors in the Transparent Controller
The SCC reports message reception and transmission errors using the channel buffer
descriptors, the error counters, and SCCE. Table 23-5 describes transmit errors.
Error
Transmitter
When this occurs, the channel stops sending the buffer, closes it, sets TxBD[UN], and generates a
Underrun
TXE interrupt if it is enabled. Transmission resumes after a
received. Underrun occurs after a transmit frame for which TxBD[L] was not set. In this case, only
SCCE[TXE] is set. Underrun cannot occur between transparent frames.
CTS Lost During
When this occurs, the channel stops sending the buffer, closes it, sets TxBD[CT], and generates
Message
the TXE interrupt if it is enabled. The channel resumes sending after
Transmission
Table 23-6 describes receive errors.
Error
Overrun
The SCC maintains a receive FIFO. The CPM starts programming the SDMA channel if the buffer is
in external memory and updating the CRC when 8 or 32 bits are received in the FIFO as determined
by GSMR_H[RFW]. If a FIFO overrun occurs, the SCC writes the received byte over the previously
received byte. The previous character and its status bits are lost. Afterwards, the channel closes the
buffer, sets OV in the BD, and generates the RXB interrupt if it is enabled. The receiver immediately
enters hunt mode.
CD Lost During
When this occurs, the channel stops receiving messages, closes the buffer, sets RxBD[CD], and
Message
generates the RXB interrupt if it is enabled. This error has highest priority. The rest of the message
Reception
is lost, and no other errors are checked in the message. The receiver immediately enters hunt
mode.
23-8
Table 23-4. Receive Commands
Description
ENTER HUNT MODE
INIT TX AND RX PARAMETERS
Table 23-5. Transmit Errors
Description
Table 23-6. Receive Errors
Description
MPC8260 PowerQUICC II UserÕs Manual
forces the transparent receiver to the current
resets receive and transmit parameters.
RESTART TRANSMIT
RESTART TRANSMIT
command is
is received.
MOTOROLA
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