www
.mcu.com.cn
211
/
239
Rev.
1.00
CMS80F731x Reference Manual
23.3 The ADC Hardware Trigger Start
In addition to software-triggered ADC conversion, the ADC module provides a way for hardware to trigger start. One is the
external port edge triggering method, and the other is the edge or periodic triggering mode of the PWM.
Using a hardware trigger ADC requires setting ADCX to 1, even if the ADC function can be triggered externally. The
hardware trigger signal will set the ADGO bit to 1 after a certain delay, and will be automatically cleared after conversion. After
the hardware trigger function is enabled, the software trigger function is not disabled, and the AD conversion can be initiated by
writing 1 to the ADGO bit when the ADC is idle.
23.3.1
The External Port Edge Triggers the ADC
The ADET pin edge automatically triggers the ADC conversion. At this point, ADTGS [1:0] needs to be 11 (select external
port edge trigger), ADEGS [1:0] can choose which edge trigger.
23.3.2
PWM Triggers the ADC
The PWM can optionally trigger the ADC conversion by the edge or the zero point. ADTGS [1:0] Select the PWM channel
(PG0, PG2, PG4), and ADEGS [1:0] can select the triggering method of edge type or period type.
23.3.3
Hardware Trigger Start Delay
After the hardware trigger signal is generated, the AD conversion is not started immediately, and it takes a certain delay
before the ADGO is set to 1. The delay is determined by ADDLY [9:0]. The delay time of the hardware trigger signal:
(ADDLY+3)*Tsys, the block diagram of the delayed trigger structure is shown in the following figure:
CLK
ADEN (ADCON1[7])
PWM0
ADGO (ADCON0[1])
Tdelay