mc9s08gt32a Freescale Semiconductor, Inc, mc9s08gt32a Datasheet - Page 192

• Manufacturer Part Number: mc9s08gt32a
• Description: Hcs08 Microcontrollers 8-bit Microcontroller Family
• Manufacturer: Freescale Semiconductor, Inc

12.2
The SPI optionally shares four port pins. The function of these pins depends on the settings of SPI control
bits. When the SPI is disabled (SPE = 0), these four pins revert to being general-purpose port I/O pins that
are not controlled by the SPI.
12.2.1
When the SPI is enabled as a slave, this pin is the serial clock input. When the SPI is enabled as a master,
this pin is the serial clock output.
12.2.2
When the SPI is enabled as a master and SPI pin control zero (SPC0) is 0 (not bidirectional mode), this
pin is the serial data output. When the SPI is enabled as a slave and SPC0 = 0, this pin is the serial data
input. If SPC0 = 1 to select single-wire bidirectional mode, and master mode is selected, this pin becomes
the bidirectional data I/O pin (MOMI). Also, the bidirectional mode output enable bit determines whether
the pin acts as an input (BIDIROE = 0) or an output (BIDIROE = 1). If SPC0 = 1 and slave mode is
selected, this pin is not used by the SPI and reverts to being a general-purpose port I/O pin.
12.2.3
When the SPI is enabled as a master and SPI pin control zero (SPC0) is 0 (not bidirectional mode), this
pin is the serial data input. When the SPI is enabled as a slave and SPC0 = 0, this pin is the serial data
output. If SPC0 = 1 to select single-wire bidirectional mode, and slave mode is selected, this pin becomes
the bidirectional data I/O pin (SISO) and the bidirectional mode output enable bit determines whether the
pin acts as an input (BIDIROE = 0) or an output (BIDIROE = 1). If SPC0 = 1 and master mode is selected,
this pin is not used by the SPI and reverts to being a general-purpose port I/O pin.
12.2.4
When the SPI is enabled as a slave, this pin is the low-true slave select input. When the SPI is enabled as
a master and mode fault enable is off (MODFEN = 0), this pin is not used by the SPI and reverts to being
a general-purpose port I/O pin. When the SPI is enabled as a master and MODFEN = 1, the slave select
output enable bit determines whether this pin acts as the mode fault input (SSOE = 0) or as the slave select
output (SSOE = 1).
192
External Signal Description
SPSCK — SPI Serial Clock
MOSI — Master Data Out, Slave Data In
MISO — Master Data In, Slave Data Out
SS — Slave Select
BUS CLOCK
SPPR2:SPPR1:SPPR0
1, 2, 3, 4, 5, 6, 7, or 8
Figure 12-4. SPI Baud Rate Generation
PRESCALER
MC9S08GB60A Data Sheet, Rev. 1.02
DIVIDE BY
2, 4, 8, 16, 32, 64, 128, or 256
CLOCK RATE DIVIDER
SPR2:SPR1:SPR0
DIVIDE BY
Freescale Semiconductor
MASTER
SPI
BIT RATE