MC68HC11F1/FC0
MOTOROLA
MC68HC11FTS/D
49
10 Serial Peripheral Interface
The serial peripheral interface (SPI) allows the MCU to communicate synchronously with peripheral de-
vices and other microprocessors. The SPI protocol facilitates rapid exchange of serial data between de-
vices in a control system. The MC68HC11F1 and MC68HC11FC0 can be set up for master or slave
operation. Standard data rates can be as high as one half of the E-clock rate when configured as mas-
ter, and as fast as the E-clock when configured as slave.
The MC68HC11FC0 has an additional control bit that allows the SPI baud rate counter to be bypassed.
This allows a master mode baud rate equal to the E-clock frequency.
10.1 SPI Block Diagram
Figure 12 SPI Block Diagram
SYSTEM CONFIGURATION
OPTION 2 REGISTER
INTERNAL
MCU CLOCK
÷
2
÷
4
÷
16
÷
32
DIVIDER
SELECT
SPRBYP
SPI CONTROL REGISTER
SPIE
SPE
DWOM
MSTR
CPHA
DOTTED LINE CONNECTIONS
8-BIT SHIFT REGISTER
READ DATA BUFFER
MSB
LSB
CLOCK
M
M
S
S
MISO
PD2
MOSI
PD3
M
S
SCK
PD4
CLOCK LOGIC
SS
PD5
SPR1
PIN CONTROL LOGIC
CPOL
SPR0
SPIF
WCOL
MODF
SPI STATUS REGISTER
SPR0
SPR1
MSTR
CPHA
CPOL
SPIE
SPE
MSTR
SPI
CONTROL
MODF
WCOL
SPIF
SPE
DWOM
MSTR
PRESENT ON MC68HC11FC0 ONLY
INTERNAL DATA BUS
SPI INTERRUPT
REQUEST