Processor Users Manual

31-6 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA
Part IV. Communications Processor Module
Table 31-3 describes the receive commands that apply to the HDLC controller.
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.
RESTART
TRANSMIT
Enables character transmission on the transmit channel. This command is expected by the HDLC
controller after a STOP TRANSMIT command, after a STOP TRANSMIT command is issued and the channel
in its FCC mode register is disabled, after a
GRACEFUL STOP TRANSMIT command, or after a transmitter
error (underrun or CTS
lost with no automatic frame retransmission). The HDLC controller resumes
sending from the current TBPTR in the channel TxBD table.
INIT TX
PARAMETERS
Initializes all transmit parameters in this serial channel parameter RAM to their reset state. This
command should only be issued when the transmitter is disabled. Notice that the INIT TX AND RX
PARAMETERS command can also be used to reset the transmit and receive parameters.
Table 31-3. Receive Commands
Command Description
ENTER HUNT
MODE
After the hardware or software is reset and the channel is enabled in the FCC mode register, the
channel is in receive enable mode and uses the Þrst BD in the table. The ENTER HUNT 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.
INIT RX
PARAMETERS
Initializes all the receive parameters in this serial channel parameter RAM to their reset state and
should be issued only when the receiver is disabled. Notice that the INIT TX AND RX PARAMETERS
command resets both receive and transmit parameters.
Table 31-4. HDLC Transmission Errors
Error Description
Transmitter
Underrun
When this error occurs, the channel terminates buffer transmission, closes the buffer, sets the
underrun (U) bit in the BD, and generates the TXE interrupt if it is enabled. The channel resumes
transmission after receiving the
RESTART TRANSMIT command.
CTS
Lost
during Frame
Transmission
When this error occurs, the channel terminates buffer transmission, closes the buffer, sets TxBD[CT],
and generates a TXE interrupt (if it is enabled). The channel resumes transmission after receiving
the
RESTART TRANSMIT command.
Table 31-2. Transmit Commands (Continued)
Command Description