mc9s08sg4 Freescale Semiconductor, Inc, mc9s08sg4 Datasheet - Page 222

• Manufacturer Part Number: mc9s08sg4
• Description: 8-bit Microcontroller Family
• Manufacturer: Freescale Semiconductor, Inc

Chapter 15 Serial Peripheral Interface (S08SPIV3)
15.2
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.
15.2.1
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.
15.2.2
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.
15.2.3
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.
15.2.4
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).
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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
MC9S08SG8 MCU Series Data Sheet, Rev. 3
Figure 15-4. SPI Baud Rate Generation
PRESCALER
DIVIDE BY
2, 4, 8, 16, 32, 64, 128,
SPR3:SPR2:SPR1:SPR0
CLOCK RATE DIVIDER
DIVIDE BY
256, or 512
Freescale Semiconductor
MASTER
SPI
BIT RATE