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M16C/5L Group, M16C/56 Group
24.3.2
A/D Conversion Start Conditions
An A/D conversion start trigger has a software trigger and an external trigger. Figure 24.4 shows A/D
Conversion Start Trigger.
ADST
ADTRG pin
ADST, TRG: Bits in the ADCON0 register
Figure 24.4
A/D Conversion Start Trigger
24.3.2.1
Software Trigger
The software trigger is enabled when the TRG bit in the ADCON0 register is 0 (software trigger).
A/D conversion starts by setting the ADST bit in the ADCON0 register to 1 (A/D conversion start).
24.3.2.2
External Trigger
The external trigger is enabled when the TRG bit in the ADCON0 register is 1 ( ADTRG trigger).
To use this trigger, set the following:
The direction bit of the port which shares a pin with ADTRG is 0 (input mode).
•
The TRG bit in the ADCON0 register is 1 ( ADTRG trigger).
•
•
The ADST bit in the ADCON0 register is 1 (A/D conversion start).
Under the above conditions, when input to the ADTRG pin is changed from high to low, A/D
conversion starts.
Set the high- and low-level durations of the pulse input to the ADTRG pin to two or more cycles of
fAD.
ADTRG input
A/D conversion
Figure 24.5
A/D Conversion Start Timing When External Trigger Input
R01UH0127EJ0110 Rev.1.10
Sep 01, 2011
TRG
0
1
1 to 1.5 fAD cycles
Start
conversion
24. A/D Converter
A/D conversion start trigger
Page 627 of 803
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