Section 12 A/D Converter
Rev. 7.00 Mar 10, 2005 page 406 of 652
REJ09B0042-0700
12.3 Operation
12.3.1 A/D Conversion Operation
The A/D converter operates by successive approximations, and yields its conversion result as 10-
bit data.
A/D conversion begins when software sets the A/D start flag (bit ADSF) to 1. Bit ADSF keeps a
value of 1 during A/D conversion, and is cleared to 0 automatically when conversion is complete.
The completion of conversion also sets bit IRRAD in interrupt request register 2 (IRR2) to 1. An
A/D conversion end interrupt is requested if bit IENAD in interrupt enable register 2 (IENR2) is
set to 1.
If the conversion time or input channel needs to be changed in the A/D mode register (AMR)
during A/D conversion, bit ADSF should first be cleared to 0, stopping the conversion operation,
in order to avoid malfunction.
12.3.2 Start of A/D Conversion by External Trigger Input
The A/D converter can be made to start A/D conversion by input of an external trigger signal.
External trigger input is enabled at pin
ADTRG
when bit IRQ4 in PMR1 is set to 1 and bit TRGE
in AMR is set to 1. Then when the input signal edge designated in bit IEG4 of interrupt edge
select register (IEGR) is detected at pin
ADTRG
, bit ADSF in ADSR will be set to 1, starting A/D
conversion.
Figure 12.2 shows the timing.
φ
Pin ADTRG
(when bit
IEG4 = 0)
DSF
A/D conversion
Figure 12.2 External Trigger Input Timing
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