MC68HC812A4 Datasheet, PDF (271/342 Pages) Motorola, Inc – 16-bit device composed of standard on-chip peripheral modules connected by an intermodule bus. Modules include

Serial Peripheral Interface (SPI)
Functional Description
15.6.5 SS Output
In master mode only, the SS pin can function as a chip-select output for
connection to the SS input of a slave. The master SS output
automatically selects the slave by going low for each transmission and
deselects the slave by going high during each idling state.
Enable the SS output by setting the master mode bit, MSTR, the
slave-select output enable bit, SSOE, and the data direction bit of the SS
pin. MSTR and SSOE are in SPI control register 1.
Table 15-1. SS Pin Configurations
Control Bits
SS Pin Function
DDRS7 SSOE
Master Mode
Slave Mode
0
0 Slave-select input with mode-fault detection
0
1
1
0
Reserved
General-purpose output
Slave-select input
1
1
Slave-select output
Advance Information
MOTOROLA
Serial Peripheral Interface (SPI)
MC68HC812A4 — Rev. 3.0
271