MC68HC58 Motorola, MC68HC58 Datasheet - Page 53

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

4.2.2.2 Servicing Sequence
4.2.2.3 SPI Exchange
MC68HC58
TECHNICAL DATA
Table 4-3 shows the types of serial transfers.
For every byte transmitted from the host to the DLC, there is a byte transferred from
the DLC to the host. Each data byte sent to the DLC is accompanied by a status byte
that is sent to the host. Each command byte sent to the DLC is accompanied by a re-
ceived data byte that is sent to the host.
The host MCU services the DLC in the following sequence:
Received data remains in the RxFIFO buffer until a flush byte command is received.
However, the flush command can accompany the read command. Each transmit data
byte must be accompanied by a command byte that designates it as a first, intermedi-
ate, or last byte.
The host MCU controls SCLK polarity and phase. The DLC is compatible with two
SCLK configurations:
The general format of the data exchange from the DLC to the host MCU is a bit-for-bit
exchange on each SCLK clock pulse. Data is read in on the passive to active level of
the SCLK, and is changed on the active to passive level of SCLK. The most significant
bit of a transfer is sent first. Figure 4-6 shows a 16-bit data transfer with low clock po-
larity. Figure 4-7 shows a 16-bit data transfer with high clock polarity.
1. Read status byte and data byte.
2. Write data byte, configuration byte, or null byte and command byte.
• SCLK polarity normally high, read data on SCLK passive to active level, change
• SCLK normally low, read data on SCLK passive to active level, change data on
data on SCLK active to passive level.
SCLK active to passive level.
This 16-bit transfer can be performed using two 8-bit transfers as
long as CS is asserted before the first 8-bit transfer begins, and re-
mains asserted until the end of the second 8-bit transfer.
1st Byte
SOMI
SIMO
—
—
2nd Byte
SIMO
SOMI
DATA LINK CONTROLLER OPERATION
—
—
Table 4-3 Serial Transfers
Transmit byte, configuration byte, or null byte
Receive byte, completion code, or null byte
NOTE
Type of Transfer
Command byte
Status byte
MOTOROLA
4-9