ISD94100 Series Technical Reference Manual
Sep 9, 2019
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6.7.6.6
PWM Counter Operation mode
The PWM counter supports two operation modes: one-shot mode and auto-reload mode. PWM
counter will operate in one-shot mode if CNTMODE (TIMERx_PWMCTL[3]) bit is set to 1, and
operate in auto-reload mode if CNTMODE bit is set to 0.
In both modes, CMP (TIMERx_PWMCMPDAT[15:0]) and PERIOD (TIMERx_PWMPERIOD[15:0])
should be written first and then set CNTEN (TIMERx_PWMCTL[0]) bit to 1 to start counter running.
In one-shot mode, PWM counter value will reload to default value according count type after one
PWM period is completed. User can write CMP to continuous one-shot operation to generate next
one-shot pulse once no matter current one-shot counter is running or completed.
In auto-reload mode, PWM counter is continuous running with current active PERIOD and CMP. If
user set PERIOD to zero in auto-reload mode, PWM counter value will reload to default value
according count type after one PWM period is completed.
6.7.6.7
PWM Comparator
The CMP (TIMERx_PWMCMPDAT[15:0]) is comparator register of PWM. The CMP value is
continuously compared to the corresponding counter value. When the counter is equal to CMP,
PWM generates a compared point event. This event will generate PWM output pulse, interrupt
signal or trigger ADC start convert. In up-down count type, two events will be generated in a PWM
period as shown in Figure 6.7-17. The CMPU is up count compared point event and CMPD is down
count compared point event.
PWMDIRF
(TIMERx_PWMCNT[16])
0
1
2
3
4
3
1
2
0
1
2
3
4
3
1
2
0
5
6
7
6
4
5
1
2
3
4
PWM Period
PERIOD = 4
CMPDAT = 4
PERIOD = 7
CMPDAT = 5
PWM Period
Up-count compared
point event (CMPU)
Down-count compared
point event (CMPD)
PERIOD = 5
CMPDAT= 0
PWMCNT
(TIMERx_PWMCNT[15:0])
Note:
No CMPU event occurred when CMPDAT equals to PERIOD.
Figure 6.7-17 PWM Comparator Events in Up-Down Count Type
6.7.6.8
Period Loading Mode
When the IMMLDEN (TIMERx_PWMCTL[9]) bit set to 0, PWM operates at period loading mode.
The PWM provides PBUF (TIMERx_PWMPBUF[15:0]) is the active PERIOD buffer register and
CMPBUF (TIMERx_PWMCMPBUF[15:0]) is the active CMP buffer register. In period loading mode,
both PERIOD (TIMERx_PWMPERIOD[15:0]) and CMP (TIMERx_PWMCMPDAT[15:0]) will load to
their active PBUF and CMPBUF register while each PWM period is completed. Figure 6.7-18 shows
period loading timing of up count type, where PERIOD DATA0 denotes the initial data of PERIOD,
