Chapter 21 Serial Peripheral Interface (S12SPIV5)
MC9S12XE-Family Reference Manual Rev. 1.19
Freescale Semiconductor
771
Table 21-9. SPIF Interrupt Flag Clearing Sequence
Table 21-10. 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
2. Data in SPIDRH is undefined in this case.
or
Byte Write to SPIDRH
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
or
Word Write to (SPIDRH:SPIDRL)
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