MC68HC05C8A Datasheet, PDF (89/158 Pages) Motorola, Inc – Microcontrollers

Serial Peripheral Interface (SPI)
SPI Signal Description
10.4.3 Serial Clock (SCK)
The master clock is used to synchronize data movement both in and out
of the device through its MOSI and MISO lines. The master and slave
devices are capable of exchanging a byte of information during a
sequence of eight clock cycles. Since SCK is generated by the master
device, this line becomes an input on a slave device.
As shown in Figure 10-1, four possible timing relationships may be
chosen by using control bits CPOL and CPHA in the serial peripheral
control register (SPCR). Both master and slave devices must operate
with the same timing. The master device always places data on the
MOSI line one-half cycle before the clock edge (SCK), so the slave
device can latch the data.
Two bits (SPR0 and SPR1) in the SPCR of the master device select the
clock rate. In a slave device, SPR0 and SPR1 have no effect on the SPI
operation.
SS
SCK
SCK
SCK
SCK
MISO/MOSI
MSB
6
5
4
3
2
1
0
INTERNAL STROBE FOR DATA CAPTURE (ALL MODES)
Figure 10-1. Data Clock Timing Diagram
MC68HC05C8A • MC68HCL05C8A • MC68HSC05C8A — Rev. 5.0
MOTOROLA
Serial Peripheral Interface (SPI)
Technical Data
89