CHAPTER 9 TIMER/COUNTER FUNCTION (REAL-TIME PULSE UNIT)
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User’s Manual U14492EJ3V0UD
(2) Overflow
When the TM3 register has counted the count clock from FFFFH to 0000H, the TM3OVF bit of the TMC30
register is set (1), and an overflow interrupt (INTTM3) is generated at the same time. However, if the CC30
register is set to compare mode (CMS0 bit = 1) and to the value FFFFH when match clearing is enabled
(CCLR bit = 1), then the TM3 register is considered to be cleared and the TM3OVF bit is not set (1) when the
TM3 register changes from FFFFH to 0000H. Also, the overflow interrupt (INTTM3) is not generated .
When the TM3 register is changed from FFFFH to 0000H because the TM3CE bit changes from 1 to 0, the
TM3 register is considered to be cleared, but the TM3OVF bit is not set (1) and no INTTM3 interrupt is
generated.
Also, timer operation can be stopped after an overflow by setting the OST bit of the TMC31 register to 1.
When the timer is stopped due to an overflow, the count operation is not restarted until the TM3CE bit of the
TMC30 register is set (1).
Operation is not affected even if the TM3CE bit is set (1) during a count operation.
Figure 9-85. Operation After Overflow (When OST = 1)
Overflow
Count
start
Overflow
FFFFH
FFFFH
TM3
0
INTTM3
OST
←
1
TM3CE
←
1
TM3CE
←
1
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