MC68HC58 Motorola, MC68HC58 Datasheet - Page 70

• Manufacturer Part Number: MC68HC58
• Description: Data Link Controller
• Manufacturer: Motorola

5.1.1.7 Abort Transmission
5.1.2 BTAD[4:2] — Byte Type and Destination Field
5.1.2.1 Do Not Load
5.1.2.2 Load as Transmit Data
5-4
MOTOROLA
If a frame is in progress on the J1850 bus (no EOD has been detected) when this com-
mand is latched, the DLC sends the IFR only if no receiver errors are detected. When
receiver errors are detected, the IFR is not transmitted, and is lost. If this occurs, the
DLC status byte indicates that the TxFIFO buffer is empty, and the DLC does not ter-
minate automatic retry.
If the DLC is transmitting when this command is latched, a timing error or an incom-
plete byte error occurs. The TxFIFO buffer is flushed, and both the frame and the IFR
are lost.
When additional IFR bytes are required, they must be placed in the TxFIFO buffer rap-
idly enough to prevent underrun. The second IFR byte must be loaded before the fall-
ing edge of the Normalization bit, and subsequent bytes must be loaded within 500 s
of each other. If a TxFIFO underrun occurs, it is flagged as an error.
The “abort transmission” command causes the transmitter to be reset immediately.
Any transmission in progress is terminated, and the TxFIFO buffer is flushed. The first
byte of a new frame can accompany this command.
The BTAD field tells the DLC how to treat the data byte that accompanies a command
byte. Table 5-2 is a summary of byte type and destination commands. Detailed dis-
cussion of each command follows.
The “do not load” command indicates to the DLC that a byte type and destination com-
mand should not be executed.
The “load as transmit data” command places an accompanying data byte in the
TxFIFO buffer for transmission.
Value
000
001
010
011
100
101
110
111
Table 5-2 Byte Type and Destination Summary
CONTROL AND STATUS CODES
Load as first and last byte of transmit data
Load as configuration byte-immediate
Load as first byte of transmit data
Load as last byte of transmit data
Load as configuration byte
Load as transmit data
Description
Do not load
Reserved
TECHNICAL DATA
MC68HC58