10
10-37
MULTIJUNCTION TIMERS
10.2 Common Units of Multijunction Timers
32180 Group User’s Manual (Rev.1.0)
b4 5 b7
Interrupt request status
Initial state
Event occurs on bit 6
Interrupt request
Event occurs on bit 4
Only bit 6 cleared
Bit 4 data retained
b4 5 b7
1 1 0 1
Write to the interrupt request status
Example for clearing interrupt request status
0 0 0 0
0 0 1 0
1 0 1 0
1 0 0 0
Program example
ISTREG = 0xfd; /* Clear ISTAT1 (0x02 bit) only */
• To clear the Interrupt Request Status Register 0 (ISTREG) interrupt request status 1, ISTAT1 (0x02 bit)
To clear an interrupt request status, always be sure to write "1" to all other interrupt request status bits. At this time,
avoid using a logic operation like the one shown below. Because it requires three step-ISTREG read, logic operation
and write, if another interrupt request occurs between the read and write, status may be inadvertently cleared.
b4 5 6 b7
Interrupt request status
Event occurs on bit 6
Event occurs on bit 4
Only bit 6 cleared
Bit 4 also cleared
0 0 1 0
1 0 1 0
0 0 0 0
Read
0 0 1 0
0 0 0 0
Clear bit 6 (ANDing with 1101)
Write
6
6
ISTREG &= 0xfd; /* Clear ISTAT1 (0x02 bit) only */
Figure 10.2.4 Example for Clearing Interrupt Request Status
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