GD32W51x User Manual
453
Figure 17-7. Timing chart of down counting mode, change TIMERx_CAR ongoing
TIMER_CK
CEN
CNT_CLK(PSC_CLK)
CNT_REG
05
04
03
02
01
00
63
62
61
60
5F
5E
5D
5C
Update event (UPE)
Update interrupt flag (UPIF)
Auto-reload register
65
63
change CAR Vaule
CNT_REG
05
04
03
02
01
00
63
01
00
65
Update event (UPE)
Update interrupt flag (UPIF)
Auto-reload register
65
63
change CAR Vaule
65
63
Auto-reload shadow register
...
Hardware set
Hardware set
Software clear
Hardware set
ARSE = 0
ARSE = 1
62
61
63
65
change CAR Vaule
64
63
65
Center-aligned counting mode
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 direction and
generates an underflow event when the counter counts to 1 in the down-counting direction.
The counting direction bit DIR in the TIMERx_CTL0 register is read-only and indicates the
counting direction when in the center-aligned mode. The counting direction is updated by
hardware automatically.
Setting the UPG bit in the TIMERx_SWEVG register will initialize the counter value to 0 and
generates an update event irrespective of whether the counter is counting up or down in the
center-align counting mode.
The UPIF bit in the TIMERx_INTF register can 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 17-8. Timing chart of center-aligned counting
If set the UPDIS bit in the TIMERx_CTL0 register, the update event is disabled.
When an update event occurs, all the registers (repetition counter, auto-reload register,