Freescale Semiconductor MPC8260 - Manual (Page 1230)

FCC HDLC Controller
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
36-6 Freescale Semiconductor
Table 36-3 describes the receive commands that apply to the HDLC controller.
36.5.2 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 36-4 describes HDLC transmission errors, which
are reported through the TxBD.
Table 36-5 describes HDLC reception errors, which are reported through the RxBD.
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 36-3. 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 first 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 flag sequence. After receiving the command, the current receive buffer is closed, the error status
flags and length field are cleared, RxBD[E] (the empty bit) is set, and the CRC calculation is reset.
Further frame reception uses the current RxBD.
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 36-4. HDLC Transmission Errors
Error Description
Transmitter
Underrun When this error occurs, the channel terminates buffer transmission, transmit an ABORT sequence
(a sequence which will generate CRC error on the frame), 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 36-2. Transmit Commands (continued)
Command Description