mc68hc908gr16 Freescale Semiconductor, Inc, mc68hc908gr16 Datasheet - Page 209

• Manufacturer Part Number: mc68hc908gr16
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

16.10.1 Wait Mode
The SPI module remains active after the execution of a WAIT instruction. In wait mode the SPI module
registers are not accessible by the CPU. Any enabled CPU interrupt request from the SPI module can
bring the MCU out of wait mode.
If SPI module functions are not required during wait mode, reduce power consumption by disabling the
SPI module before executing the WAIT instruction.
To exit wait mode when an overflow condition occurs, enable the OVRF bit to generate CPU interrupt
requests by setting the error interrupt enable bit (ERRIE). See
16.10.2 Stop Mode
The SPI module is inactive after the execution of a STOP instruction. The STOP instruction does not
affect register conditions. SPI operation resumes after an external interrupt. If stop mode is exited by
reset, any transfer in progress is aborted, and the SPI is reset.
16.11 SPI During Break Interrupts
The system integration module (SIM) controls whether status bits in other modules can be cleared during
the break state. The BCFE bit in the SIM break flag control register (SBFCR) enables software to clear
status bits during the break state. See
To allow software to clear status bits during a break interrupt, write a 1 to the BCFE bit. If a status bit is
cleared during the break state, it remains cleared when the MCU exits the break state.
To protect status bits during the break state, write a 0 to the BCFE bit. With BCFE at 0 (its default state),
software can read and write I/O registers during the break state without affecting status bits. Some status
bits have a 2-step read/write clearing procedure. If software does the first step on such a bit before the
break, the bit cannot change during the break state as long as BCFE is at logic 0. After the break, doing
the second step clears the status bit.
Since the SPTE bit cannot be cleared during a break with the BCFE bit cleared, a write to the transmit
data register in break mode does not initiate a transmission nor is this data transferred into the shift
register. Therefore, a write to the SPDR in break mode with the BCFE bit cleared has no effect.
16.12 I/O Signals
The SPI module has five I/O pins and shares four of them with a parallel I/O port. They are:
The SPI has limited inter-integrated circuit (I
single-master environment. To communicate with I
when the SPWOM bit in the SPI control register is set. In I
are connected to a bidirectional pin from the I
Freescale Semiconductor
•
•
•
•
•
MISO — Data received
MOSI — Data transmitted
SPSCK — Serial clock
SS — Slave select
CGND — Clock ground (internally connected to V
MC68HC908GR16 Data Sheet, Rev. 5.0
Chapter 15 System Integration Module (SIM).
2
C) capability (requiring software support) as a master in a
2
C peripheral and through a pullup resistor to V
2
C peripherals, MOSI becomes an open-drain output
SS
2
)
C communication, the MOSI and MISO pins
16.8
Interrupts.
SPI During Break Interrupts
DD
.
209