MC68HC58 Motorola, MC68HC58 Datasheet - Page 50

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

4.2.1.2 Servicing Sequence
4-6
MOTOROLA
DLC command bytes are transferred before the accompanying data byte. When using
the parallel host interface, the DLC requires command bytes only for the first and last
byte(s) in a frame. A DLC command byte must be accompanied by another byte (data,
null, or configuration) in order for the command to be latched. A command byte is not
required to load each data byte into the TxFIFO buffer, but a data byte is required for
a command to execute. Table 4-1 shows the types of parallel transfers.
The status byte value is frozen while CS is asserted. Any changes that occur while CS
is asserted are reflected in the status byte when CS is next asserted.
The DLC interrupt request line is cleared when CS is asserted and the status byte is
read. When CS is negated, the DLC parallel lines are disabled, and go into a high im-
pedance state.
The host MCU services the DLC in the following sequence:
The four operations form a complete service sequence. However, all four operations
are not required in every host/DLC transfer.
ADDR0
R/W=0
R/W=1
1. Read status byte.
2. Read receive data (if required).
3. Write command byte.
4. Write transmit data, configuration, or null byte (if preceded by command byte).
ADDR0
COMMAND BYTE[7:0]
STATUS BYTE[7:0]
0
0
1
1
Figure 4-4 Parallel Mode Byte Format
DATA LINK CONTROLLER OPERATION
Table 4-1 Parallel Transfers
R/W
0
1
0
1
Transmit byte or configuration byte
Receive byte or completion code
Type of Transfer
Command byte
Status byte
TRANSMIT BYTE[7:0]
RECEIVE BYTE[7:0]
TECHNICAL DATA
DLC PARALLEL BYTE FORMAT
MC68HC58