MPC8280 datasheet(1268/1386 Pages) FREESCALE

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FCC HDLC Controller

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

37-6

Freescale Semiconductor

Table 37-3 describes the receive commands that apply to the HDLC controller.

37.5.2

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 37-4 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 37-3. 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 37-4. 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 37-2. Transmit Commands (continued)

Command

Description

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