Handling Errors In The Asynchronous Hdlc Controller - Freescale Semiconductor MPC850 User Manual

Handling Errors in the Asynchronous HDLC Controller

Command
Sends the asynchronous HDLC abort sequence (0x7D;0x7E for PPP, 0x7D; 0xC1 for IrLAP) and
STOP
disables data transmission. If the asynchronous HDLC controller receives this command during
TRANSMIT
frame transmission, the abort sequence is put in the FIFO and the transmitter does not try to send
more data from the current BD or advance to the next TxBD. The BD to be terminated is indicated
by the TBPTR entry in the parameter RAM table.
Note that unlike with other SCC protocols, the
Up to 16 characters (32 on SCC2) can be sent ahead of the abort sequence unless GSMR_H[TFL]
= 1.
Not supported by the asynchronous HDLC controller.
GRACEFUL
STOP
TRANSMIT
Reenables transmission of characters; the asynchronous HDLC controller expects it after a
RESTART
TRANSMIT TRANSMIT
the buffer using the current TxBD (pointed to by TBPTR).
Initializes all Tx parameters in this channel's parameter RAM to reset state. It must be issued only
INIT TX
when the transmitter is disabled. The
PARAMETERS
parameters.
Table 25-4 describes receive commands. After hardware or software is reset and a channel
is enabled in the GSMR, reception begins with the first BD in the RxBD table.
Command
Forces the asynchronous HDLC controller to close the current RxBD, if it is in use, and enter hunt
ENTER HUNT
mode. Reception resumes after the controller finds a frame preceded by one or more opening flags.
MODE
Not supported by the asynchronous HDLC controller.
CLOSE RXBD
Initializes all Rx parameters in the channel's parameter RAM to reset state. Issue only when the
INIT RX
receiver is disabled. The
PARAMETERS
25.12 Handling Errors in the Asynchronous HDLC
Controller
The asynchronous HDLC controller reports frame reception and transmission error
conditions using the channel BDs and the asynchronous HDLC event register (SCCE).
Table 25-5 describes transmit errors.
Error
CTS Lost during The channel stops sending the buffer, closes it, sets SCCE[TXE] and TxBD[CT]. The channel
Frame resumes sending from the next TxBD after a
Transmission
Table 25-3. Transmit Commands
command or transmitter error. The controller continues sending from the first character in
Table 25-4. Receive Commands
INIT TX AND RX PARAMETERS
Table 25-5. Transmit Errors
MPC850 Family User's Manual
Description
command does not flush the FIFO.
STOP TRANSMIT
INIT TX AND RX PARAMETERS
Description
command resets both Tx and Rx parameters.
Description
RESTART TRANSMIT
command resets both Tx and Rx
command is issued.
STOP