Serial Peripheral Interface (S12SPIV5)
MC9S12XHY-Family Reference Manual Rev. 1.01
Freescale Semiconductor
503
Table 15-8. SPIF Interrupt Flag Clearing Sequence
Table 15-9. SPTEF Interrupt Flag Clearing Sequence
XFRW Bit
SPIF Interrupt Flag Clearing Sequence
0
Read SPISR with SPIF == 1
then
Read SPIDRL
1
Read SPISR with SPIF == 1
then
Byte Read SPIDRL
1
1
Data in SPIDRH is lost in this case.
or
Byte Read SPIDRH
2
2
SPIDRH can be read repeatedly without any effect on SPIF. SPIF Flag is cleared only by the read
of SPIDRL after reading SPISR with SPIF == 1.
Byte Read SPIDRL
or
Word Read (SPIDRH:SPIDRL)
XFRW Bit
SPTEF Interrupt Flag Clearing Sequence
0
Read SPISR with SPTEF == 1 then
Write to SPIDRL
1
1
Any write to SPIDRH or SPIDRL with SPTEF == 0 is effectively ignored.
1
Read SPISR with SPTEF == 1
then
Byte Write to SPIDRL
12
2
Data in SPIDRH is undefined in this case.
or
Byte Write to SPIDRH
13
3
SPIDRH can be written repeatedly without any effect on SPTEF. SPTEF Flag is cleared only by
writing to SPIDRL after reading SPISR with SPTEF == 1.
Byte Write to SPIDRL
1
or
Word Write to (SPIDRH:SPIDRL)
1
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