MC68HC08AZ0 Datasheet, PDF (239/444 Pages) Motorola, Inc – Advance Information

Freescale Semiconductor, Inc.
Serial Peripheral Interface Module (SPI)
Resetting the SPI
Resetting the SPI
Any system reset completely resets the SPI. Partial resets occur
whenever the SPI enable bit (SPE) is low. Whenever SPE is low, the
following occurs:
• The SPTE flag is set
• Any transmission currently in progress is aborted
• The shift register is cleared
• The SPI state counter is cleared, making it ready for a new
complete transmission
• All the SPI port logic is defaulted back to being general purpose
I/O.
The following items are reset only by a system reset:
• All control bits in the SPCR register
• All control bits in the SPSCR register (MODFEN, ERRIE, SPR1,
and SPR0)
• The status flags SPRF, OVRF, and MODF
By not resetting the control bits when SPE is low, the user can clear SPE
between transmissions without having to set all control bits again when
SPE is set back high for the next transmission.
By not resetting the SPRF, OVRF, and MODF flags, the user can still
service these interrupts after the SPI has been disabled. The user can
disable the SPI by writing ‘0’ to the SPE bit. The SPI can also be disabled
by a mode fault occurring in an SPI that was configured as a master with
the MODFEN bit set.
21-spi
MOTOROLA
Serial Peripheral Interface Module (SPI)
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MC68HC08AZ0
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