Serial Peripheral Interface Module (SPI)
Technical Data
MC68HC908AB32
—
Rev. 1.0
296
Serial Peripheral Interface Module (SPI)
MOTOROLA
slave. This happens because SS at logic 0 indicates the start of the
transmission (MISO driven out with the value of MSB) for CPHA = 0.
When CPHA = 1, a slave can be selected and then later unselected with
no transmission occurring. Therefore, MODF does not occur since a
transmission was never begun.
In a slave SPI (MSTR = 0), the MODF bit generates an SPI
receiver/error CPU interrupt request if the ERRIE bit is set. The MODF
bit does not clear the SPE bit or reset the SPI in any way. Software can
abort the SPI transmission by clearing the SPE bit of the slave.
NOTE:
A logic 1 voltage on the SS pin of a slave SPI puts the MISO pin in a high
impedance state. Also, the slave SPI ignores all incoming SPSCK
clocks, even if it was already in the middle of a transmission.
To clear the MODF flag, read the SPSCR with the MODF bit set and then
write to the SPCR register. This entire clearing mechanism must occur
with no MODF condition existing or else the flag is not cleared.
16.9 Interrupts
Four SPI status flags can be enabled to generate CPU interrupt
requests.
Table 16-2. SPI Interrupts
Flag
Request
SPTE
Transmitter empty
SPI transmitter CPU interrupt request
(SPTIE = 1, SPE = 1)
SPRF
Receiver full
SPI receiver CPU interrupt request
(SPRIE = 1)
OVRF
Overflow
SPI receiver/error interrupt request (ERRIE = 1)
MODF
Mode fault
SPI receiver/error interrupt request (ERRIE = 1)
Summary of Contents for MC68HC908AB32
Page 1: ...MC68HC908AB32 D REV 1 0 MC68HC908AB32 HCMOS Microcontroller Unit TECHNICAL DATA ...
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Page 68: ...FLASH Memory Technical Data MC68HC908AB32 Rev 1 0 68 FLASH Memory MOTOROLA ...
Page 84: ...EEPROM Technical Data MC68HC908AB32 Rev 1 0 84 EEPROM MOTOROLA ...
Page 390: ...Ordering Information Technical Data MC68HC908AB32 Rev 1 0 390 Ordering Information MOTOROLA ...
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