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M16C/29 Group
15.6 Precautions of Using A/D Converter
(1) Set the bit in the port direction register, which corresponds to the pin being used as the analog input,
to "0" (input mode) Set the bit in the port direction register, which corresponds to pin AD
(input mode) if the external trigger is used.
(2) When using a key input interrupt, do not use pins AN
request is generated when the A/D input voltage is "L" ).
(3) Insert capacitors between pins AV
to prevent latch-ups and malfunctions due to noise, and to minimize conversion errors. The same
applies to pins V
(4) Incorrect values are stored in the ADi register (i=0 to 7) if the CPU reads the ADi register while the ADi
register is storing results from a completed A/D conversion. This occurs when a divided main clock or
a sub clock is selected as the CPU clock.
• In one-shot mode or single sweep mode, simultaneous sample sweep mode and delayed trigger
mode 0, 1 , read the corresponding ADi register after verifying that the A/D conversion has been
completed. (The completion of the A/D conversion can be determined by the IR bit in the ADIC
register).
• In repeat mode, repeat sweep mode 0 and repeat sweep mode 1, use an undivided main clock as
the CPU clock.
(5) Conversion results of the A/D converter are indeterminate, if the ADST bit in the ADCON0 register is
set to "0" (A/D conversion halted) and the conversion is forcibly terminated, by program during A/D
conversion. ADi registers not operating A/D conversion may also be indeterminate. If the ADST bit is
changed to "0" by program, during the A/D conversion, do not use any values obtained from the ADi
registers.
Figure 15.6.1 VCC, VSS, AVCC, AVSS, VREF and ANi Connections
Rev.1.00 Nov 01,2004
REJ09B0101-0100Z
, V
CC
and V
. Figure 15.6.1 shows the procedure of each pin.
CC
SS
Microcomputer
AV
V
AV
V
CC
C4
V
SS
AN
: AN
(i=0 to 7), AN
(i=0 to 7 for 80-pin version, and i=0 to 3 for 64-pin version)
i
i
0i
AN
(i=0 to 7 for 80-pin version, i=4 for 64-pin version), AN
2i
NOTES
1. C1≥0.47µF, C2≥0.47µF, C3≥100pF, C4≥0.1µF (reference)
2. Use thick and shortest possible wiring to connect capacitors.
page 246 of 402
to AN
as analog input pins (key input interrupt
4
7
, analog input pin (AN
REF
CC
REF
C2
C1
SS
C3
AN
i
15. A/D Converter
(i=0 to 7), AN
and AN
i
0i
(i=0 to 2)
3i
, to "0"
TRG
) and AV
2i
SS
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