GD32A50x User Manual
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Figure 18-5. Timing chart of up counting mode, change TIMERx_CAR on the go
TIMER_CK
CEN
PSC_CLK
CNT_REG
94
95
96
97
98
99
0
1
2
3
4
5
6
7
Update event (UPE)
Update interrupt flag (UPIF)
Auto-reload register
120
99
change CAR Vaule
CNT_REG
113
114 115 116 117 118
119 120
0
1
2
98
99
0
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
Counter down counting
In this mode, the counter counts down continuously from the counter-reload value, which is
defined in the TIMERx_CAR register, to 0 in a count-down direction. Once the counter
reaches to 0, the counter the counter will start counting down from the counter-reload value
again and an underflow event will be generated. In addition, the update event will be
generated after (TIME1) times of underflow. The counting direction bit DIR in the
TIMERx_CTL0 register should be set to 1 for the down-counting mode.
When the update event is set by the UPG bit in the TIMERx_SWEVG register, the counter
value will be initialized to the counter reload value and an update event will be generated.
If the UPDIS bit in TIMERx_CTL0 register is set, the update event is disabled.
When an update event occurs, all the shadow registers (repetition counter register, counter
auto reload register, prescaler register) are updated.
Figure 18-6. Timing chart of down counting mode, PSC=0/2
and