MC9S08QG8 Datasheet, PDF (218/300 Pages) Freescale Semiconductor, Inc – 8-BIT HCS08 Central Processor Unit

Serial Peripheral Interface (S08SPIV3)
Table 15-1. SPIC1 Field Descriptions (continued)
Field
1
SSOE
0
LSBFE
Description
Slave Select Output Enable — This bit is used in combination with the mode fault enable (MODFEN) bit in
SPIC2 and the master/slave (MSTR) control bit to determine the function of the SS pin as shown in Table 15-2.
LSB First (Shifter Direction)
0 SPI serial data transfers start with most significant bit
1 SPI serial data transfers start with least significant bit
MODFEN
0
0
1
1
SSOE
0
1
0
1
Table 15-2. SS Pin Function
Master Mode
General-purpose I/O (not SPI)
General-purpose I/O (not SPI)
SS input for mode fault
Automatic SS output
Slave Mode
Slave select input
Slave select input
Slave select input
Slave select input
15.3.2 SPI Control Register 2 (SPIC2)
This read/write register is used to control optional features of the SPI system. Bits 7, 6, 5, and 2 are not
implemented and always read 0.
7
6
5
4
3
2
R
0
0
0
0
MODFEN BIDIROE
W
Reset
0
0
0
0
0
0
= Unimplemented or Reserved
Figure 15-6. SPI Control Register 2 (SPIC2)
1
SPISWAI
0
0
SPC0
0
Table 15-3. SPIC2 Register Field Descriptions
Field
Description
4
MODFEN
Master Mode-Fault Function Enable — When the SPI is configured for slave mode, this bit has no meaning or
effect. (The SS pin is the slave select input.) In master mode, this bit determines how the SS pin is used (refer
to Table 15-2 for more details).
0 Mode fault function disabled, master SS pin reverts to general-purpose I/O not controlled by SPI
1 Mode fault function enabled, master SS pin acts as the mode fault input or the slave select output
3
BIDIROE
Bidirectional Mode Output Enable — When bidirectional mode is enabled by SPI pin control 0 (SPC0) = 1,
BIDIROE determines whether the SPI data output driver is enabled to the single bidirectional SPI I/O pin.
Depending on whether the SPI is configured as a master or a slave, it uses either the MOSI (MOMI) or MISO
(SISO) pin, respectively, as the single SPI data I/O pin. When SPC0 = 0, BIDIROE has no meaning or effect.
0 Output driver disabled so SPI data I/O pin acts as an input
1 SPI I/O pin enabled as an output
MC9S08QG8 and MC9S08QG4 Data Sheet, Rev. 1.01
218
Freescale Semiconductor