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GD32F403xx User Manual
312
Figure 16-33. 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 f rom the counter-reload value, which is
def ined in the TIMERx_CAR register, to 0 in a count-down direction. Once the counter
reaches to 0, the counter will start counting down from the counter-reload value. The update
event is generated at each counter underf low. 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 generates an update event.
If the UPDIS bit in TIMERx_CTL0 register is set, the update event is disabled.
When an update event occurs, all the shadow registers (counter auto reload register,
prescaler register) are updated.
Figure 16-34. Timing chart of down counting mode, PSC=0/2
show some examples of the
counter behavior for different clock frequencies when TIMERx_CAR=0x99.