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GD32A50x User Manual
426
Figure 18-48.
Timing chart of down counting mode, change TIMERx_CAR on the go
TIMER_CK
CEN
PSC_CLK
CNT_REG
5
4
3
2
1
0
99
98
97
96
95
94
93
92
Update event (UPE)
Update interrupt flag (UPIF)
Auto-reload register
120
99
change CAR Vaule
CNT_REG
5
4
3
2
1
0
99
1
0
120
Update event (UPE)
Update interrupt flag (UPIF)
Auto-reload register
120
99
change CAR Vaule
120
99
Auto-reload shadow register
...
Hardware set
Hardware set
Software clear
Hardware set
ARSE = 0
ARSE = 1
98
97
120
change CAR Vaule
119 118
120
Counter center-aligned counting
In the center-aligned counting mode, the counter counts up from 0 to the counter-reload value
and then counts down to 0 alternatively. The TIMER module generates an overflow event
when the counter counts to the counter-reload value subtract 1 in the up-counting mode and
generates an underflow event when the counter counts to 1 in the down-counting mode. The
counting direction bit DIR in the TIMERx_CTL0 register is read-only and indicates the
counting direction when in the center-aligned mode.
Setting the UPG bit in the TIMERx_SWEVG register will initialize the counter value to 0 and
generate an update event irrespective of whether the counter is counting up or down in the
center-aligned counting mode.
The UPIF bit in the TIMERx_INTF register will be set to 1 either when an underflow event or
an overflow event occurs. While the CHxIF bit is associated with the value of CAM in
TIMERx_CTL0. The details refer to
Figure 18-49. Timing chart of center-aligned counting
If the UPDIS bit in the TIMERx_CTL0 register is set, the update event is disabled.
When an update event occurs, all the shadow registers (counter autoreload register, prescaler
register) are updated.