MC68HC58 Motorola, MC68HC58 Datasheet - Page 52

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

4.2.2 MC68HC58 DLC Serial Mode Host MCU Interface
4.2.2.1 Serial Mode Data Transfer
4-8
MOTOROLA
In serial mode, the MC68HC58 DLC communicates with the host MCU via the SPI.
The SPI performs simultaneous bidirectional transfers initiated by an SPI bus master,
with the DLC functioning as an SPI slave device. SPI transfers are timed by the SCLK
signal from the host MCU. All Motorola MCU families (M68HC05, M68HC08,
M68HC11, M68HC12, M68HC16, M68300 and MPC500) have devices with SPI ca-
pabilities, but any host MCU that meets the clock specification can be used. Refer to
APPENDIX A ELECTRICAL CHARACTERISTICS for more information.
Data is always transferred between the host MCU and the DLC in a two byte format,
with an optional delay between bytes for data management. This delay can be omitted
if the host is utilizing a 16-bit shift register. The CS signal must remain asserted
throughout the duration of the 16-bit transfer.
While the host MCU is transmitting a data byte to the DLC, the DLC is transmitting a
status byte to the host MCU. This status byte updates the host MCU as to the status
of the DLC and its FIFO buffers. The host MCU then transmits a command byte to the
DLC, which tells the DLC what to do with the preceding data byte, while the DLC trans-
mits a data byte to the host MCU. In the DLC, when the RFS field indicates that a com-
pletion code is at the head of the buffer, the accompanying data byte contains that
same completion code.
The command, status and data bytes are ordered MSB-to-LSB, and are transmitted in
the non-return to zero (NRZ) bit format. Figure 4-5 shows the DLC serial mode byte
format.
SCLK
SIMO
SOMI
T7
S7
S6
T6
Figure 4-5 DLC Serial Mode Byte Format
T5
S5
TRANSMIT BYTE
STATUS BYTE
T4
S4
DATA LINK CONTROLLER OPERATION
S3
T3
T2
S2
T1
S1
S0
T0
C7
R7
C6
R6
OPTIONAL DELAY FOR
DATA MANAGEMENT
C5
R5
COMMAND BYTE
RECEIVE BYTE
C4
R4
C3
R3
C2
R2
C1
R1
TECHNICAL DATA
DLC SERIAL MODE BYTE FORMAT
C0
R0
MC68HC58