Hdlc Error Handling - Motorola MPC8260 PowerQUICC II User Manual

Part IV. Communications Processor Module
Command
Enables character transmission on the transmit channel. This command is expected by the HDLC
RESTART
controller after a
TRANSMIT
in its FCC mode register is disabled, after a
error (underrun or CTS lost with no automatic frame retransmission). The HDLC controller resumes
sending from the current TBPTR in the channel TxBD table.
Initializes all transmit parameters in this serial channel parameter RAM to their reset state. This
INIT TX
command should only be issued when the transmitter is disabled. Notice that the
PARAMETERS
PARAMETERS
Table 31-3 describes the receive commands that apply to the HDLC controller.
Command
After the hardware or software is reset and the channel is enabled in the FCC mode register, the
ENTER HUNT
channel is in receive enable mode and uses the Þrst BD in the table. The
MODE
command is generally used to force the HDLC receiver to abort reception of the current frame and
enter the hunt mode. In hunt mode, the HDLC controller continually scans the input data stream for
the ßag sequence. After receiving the command, the current receive buffer is closed and the CRC is
reset. Further frame reception uses the next BD.
Initializes all the receive parameters in this serial channel parameter RAM to their reset state and
INIT RX
should be issued only when the receiver is disabled. Notice that the
PARAMETERS
command resets both receive and transmit parameters.

31.5.2 HDLC Error Handling

The HDLC controller reports frame reception and transmission error conditions using the
channel BDs, error counters, and HDLC event register (FCCE). Table 31-4 describes
HDLC transmission errors, which are reported through the TxBD.
Error
Transmitter When this error occurs, the channel terminates buffer transmission, closes the buffer, sets the
Underrun underrun (U) bit in the BD, and generates the TXE interrupt if it is enabled. The channel resumes
transmission after receiving the
CTS Lost When this error occurs, the channel terminates buffer transmission, closes the buffer, sets TxBD[CT],
during Frame and generates a TXE interrupt (if it is enabled). The channel resumes transmission after receiving
Transmission the
RESTART TRANSMIT
31-6
Table 31-2. Transmit Commands (Continued)
command, after a
STOP TRANSMIT
command can also be used to reset the transmit and receive parameters.
Table 31-3. Receive Commands
Table 31-4. HDLC Transmission Errors
RESTART TRANSMIT
command.
MPC8260 PowerQUICC II UserÕs Manual
Description
command is issued and the channel
STOP TRANSMIT
command, or after a transmitter
GRACEFUL STOP TRANSMIT
Description
INIT TX AND RX PARAMETERS
Description
command.
INIT TX AND RX
ENTER HUNT MODE
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