s908gr32ag3vfa Freescale Semiconductor, Inc, s908gr32ag3vfa Datasheet - Page 211

• Manufacturer Part Number: s908gr32ag3vfa
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Freescale Semiconductor
SPSCR
OVRF
READ
READ
SPDR
SPRF
SPI RECEIVE
COMPLETE
Figure 15-11. Clearing SPRF When OVRF Interrupt Is Not Enabled
MC68HC908GR60A • MC68HC908GR48A • MC68HC908GR32A Data Sheet, Rev. 5
SPSCR
1
2
3
4
BYTE 1
OVRF
READ
READ
SPDR
SPRF
BYTE 1 SETS SPRF BIT.
CPU READS SPSCR WITH SPRF BIT SET
AND OVRF BIT CLEAR.
CPU READS BYTE 1 IN SPDR,
CLEARING SPRF BIT.
BYTE 2 SETS SPRF BIT.
1
1
2
3
4
5
6
7
BYTE 1
Figure 15-10. Missed Read of Overflow Condition
2
BYTE 2 SETS SPRF BIT.
CPU READS SPSCR WITH SPRF BIT SET
AND OVRF BIT CLEAR.
BYTE 3 SETS OVRF BIT. BYTE 3 IS LOST.
BYTE 1 SETS SPRF BIT.
CPU READS SPSCR WITH SPRF BIT SET
AND OVRF BIT CLEAR.
CPU READS BYTE 1 IN SPDR,
CLEARING SPRF BIT.
CPU READS SPSCR AGAIN
TO CHECK OVRF BIT.
1
2
3
3
BYTE 2
4
BYTE 2
4
5
BYTE 3
BYTE 3
5
5
6
7
8
6
6
CPU READS SPSCR WITH SPRF BIT SET
AND OVRF BIT CLEAR.
BYTE 3 SETS OVRF BIT. BYTE 3 IS LOST.
CPU READS BYTE 2 IN SPDR, CLEARING SPRF BIT,
BUT NOT OVRF BIT.
BYTE 4 FAILS TO SET SPRF BIT BECAUSE
OVRF BIT IS NOT CLEARED. BYTE 4 IS LOST.
7
7
8
10
11
12
13
14
8
9
CPU READS SPSCR AGAIN
TO CHECK OVRF BIT.
CPU READS BYTE 2 SPDR,
CLEARING OVRF BIT.
BYTE 4 SETS SPRF BIT.
CPU READS SPSCR.
CPU READS BYTE 4 IN SPDR,
CLEARING SPRF BIT.
CPU READS SPSCR AGAIN
TO CHECK OVRF BIT.
CPU READS BYTE 2 IN SPDR,
CLEARING SPRF BIT.
9
BYTE 4
BYTE 4
10
11
8
12
13
14
Error Conditions
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