R01UH0092EJ0110 Rev.1.10
Page 628 of 807
Jul 31, 2012
M16C/64C Group
27. A/D Converter
27.3.2
A/D Conversion Start Conditions
An A/D conversion start trigger has a software trigger and an external trigger. Figure 27.4 shows A/D
Conversion Start Trigger.
Figure 27.4
A/D Conversion Start Trigger
27.3.2.1
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).
27.3.2.2
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.
Figure 27.5
A/D Conversion Start Timing When External Trigger Input
0
1
ADST
ADTRG pin
TRG
A/D conversion start trigger
ADST, TRG: Bits in the ADCON0 register
ADTRG input
1 to 1.5 fAD cycles
A/D conversion
Start
conversion
Содержание M16C Series
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