MC68HC58 Motorola, MC68HC58 Datasheet - Page 71

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

5.1.2.3 Load as Last Byte of Transmit Data
5.1.2.4 Load as Configuration Byte
5.1.2.5 Load as First Byte of Transmit Data
5.1.2.6 Load as Configuration Byte – Immediate
MC68HC58
TECHNICAL DATA
If this command is latched while the TxFIFO buffer is full during a block mode transfer,
the data byte is not loaded and is lost.
If this command is latched while a previously loaded complete frame is being transmit-
ted, or is in the TxFIFO buffer awaiting transmission, the data byte is not loaded and
is lost.
If this command is latched when the TxFIFO buffer is empty, the data byte is not load-
ed and is lost.
The “load as last byte of transmit data” command indicates that the accompanying
data byte is the last byte of a frame. After the byte is placed in the TxFIFO buffer for
transmission, the TxFIFO status field (TMFS) in the status byte is configured to %11
(TxFIFO full).
If this command is latched while a previously loaded complete frame is being transmit-
ted, the accompanying data byte is discarded.
If this command is latched when the TxFIFO buffer is empty, the accompanying data
byte is discarded.
The “load as configuration byte” command indicates that the accompanying data byte
contains DLC configuration data. Changes in configuration are performed after current
J1850 bus activity is finished unless this command immediately follows reset. In this
case, the DLC is configured at least 1.2 ms after the command is latched.
The “load as first byte of transmit data” command indicates that the accompanying
data byte is the first byte of a frame. After the byte is placed in the TxFIFO buffer for
transmission, the TMFS in the status byte is set to %01 (TxFIFO contains data byte).
If the transmitter encounters another “first byte” command in the buffer before decod-
ing a valid “last byte” command, it sends a complemented CRC and halts. A comple-
tion code with the error flag (ERRF) bit set and a transmitter status (TMS) field value
of %10 (transmitter underrun) is placed in the RxFIFO buffer. The second “first byte”
command and any succeeding bytes are not transmitted.
If this command is latched while a previously loaded complete frame is being transmit-
ted, the data byte is not loaded and is lost.
The “load as configuration byte – immediate” command indicates that the accompany-
ing data byte contains DLC configuration data. Changes in configuration are per-
formed immediately. This command should only be used for system initialization and
test.
CONTROL AND STATUS CODES
MOTOROLA
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