
236
CHAPTER 9 A/D CONVERTER
(2) 4-buffer mode (External trigger select: 4-buffer)
A/D converts one analog input four times using the ADTRG signal as a trigger and stores the results in four
ADCRn registers. The INTAD interrupt is generated and conversion ends when the four A/D conversions end.
While the CE bit of the ADM0 register is 1, the A/D conversion is repeated every time a trigger is input from
the ADTRG pin.
This mode is suitable for applications which calculate the average of the A/D conversion result.
Trigger
Analog Input
A/D Conversion Result Register
ADTRG signal
ANIn
ADCR0
ADTRG signal
ANIn
ADCR1
ADTRG signal
ANIn
ADCR2
ADTRG signal
ANIn
ADCR3
Remark
n = 0 to 3
ANI0
ANI1
ANI2
ANI3
ANI4
ANI5
ANI6
ANI7
ADCR0
ADCR1
ADCR2
ADCR3
ADCR4
ADCR5
ADCR6
ADCR7
A/D Converter
ADTRG
(
×
4)
(
×
4)
Figure 9-16. Examples of 4-Buffer Mode (External Trigger Select 4-Buffer) Operation
Caution Analog inputs enclosed by dotted line are not available in timer trigger and external trigger
modes.
9.7.2 Scan mode operations (External trigger scan)
Selects the analog inputs specified by the ADM0 register sequentially from the ANI0 pin using the ADTRG signal
as a trigger, and A/D converts them. The A/D conversion results are stored in the ADCRn register corresponding
to the analog input (n = 0 to 7).
When the lower 4 channels (ANI0 to ANI3) of the analog input are set so that they are scanned in the ADM0 register,
the INTAD interrupt is generated when the number of A/D conversions specified end, and A/D conversion is ended.
When the higher 4 channels (ANI0 to ANI7) of the analog input are set so that they are scanned in the ADM0 register,
after the conversion of the lower 4 channels is ended, the mode is shifted to the A/D trigger mode, and the remaining
A/D conversions are executed. The conversion results are stored in the ADCRn register corresponding to the analog
input. When the conversion of all the specified analog inputs ends, the INTAD interrupt is generated and A/D
conversion is ended.
When a trigger is input to the ADTRG pin while the CE bit of the ADM0 register is 1, the A/D conversion is started
again.
This mode is suitable for applications which continuously monitor two or more analog inputs.