mc68hc708mp16 Freescale Semiconductor, Inc, mc68hc708mp16 Datasheet - Page 267

• Manufacturer Part Number: mc68hc708mp16
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

13.8.2 Mode Fault Error
MC68HC708MP16
Freescale Semiconductor
NOTE:
—
Rev. 3.1
Setting the SPMSTR bit selects master mode and configures the
SPSCK and MOSI pins as outputs and the MISO pin as an input.
Clearing SPMSTR selects slave mode and configures the SPSCK and
MOSI pins as inputs and the MISO pin as an output. The mode fault bit,
MODF, becomes set any time the state of the slave select pin, SS, is
inconsistent with the mode selected by SPMSTR. To prevent SPI pin
contention and damage to the MCU, a mode fault error occurs if:
For the MODF flag to be set, the mode fault error enable bit (MODFEN)
must be set. Clearing the MODFEN bit does not clear the MODF flag but
does prevent MODF from being set again after MODF is cleared.
MODF generates a receiver/error CPU interrupt request if the error
interrupt enable bit (ERRIE) is also set. When the DMAS bit is low, the
SPRF, MODF, and OVRF interrupts share the same CPU interrupt
vector. (See
individually to generate a receiver/error CPU interrupt request. However,
leaving MODFEN low prevents MODF from being set.
In a master SPI with the mode fault enable bit (MODFEN) set, the mode
fault flag (MODF) is set if SS goes to logic 0. A mode fault in a master
SPI causes the following events to occur:
To prevent bus contention with another master SPI after a mode fault
error, clear all SPI bits of the data direction register of the shared I/O port
before enabling the SPI.
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The SS pin of a slave SPI goes high during a transmission
The SS pin of a master SPI goes low at any time.
If ERRIE = 1, the SPI generates an SPI receiver/error CPU
interrupt request.
The SPE bit is cleared.
The SPTE bit is set.
The SPI state counter is cleared.
The data direction register of the shared I/O port regains control of
port drivers.
Serial Peripheral Interface Module (SPI)
Figure
13-11.) It is not possible to enable MODF or OVRF
Serial Peripheral Interface Module (SPI)
Technical Data
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