A-D Converter Methods; A/D Conversion Method. 10-Bit Mode - Renesas M16C Series User Manual
16-bit single-chip microcomputer
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2.6.4 A-D Converter Methods
2.6.4.1 A/D Conversion method. 10-bit mode
The A-D converter compares the reference voltage (V
of the successive comparison register with the analog input voltage (V
Each bit of the comparison result is stored in the successive comparison register until the analog-to-
digital conversion (successive comparison method) is complete. If a trigger occurs, the A-D converter
carries out the following:
1. Fixes bit 9 of the successive comparison register.
Compares V
with V
REF
"1000000000
"(default).]
2
Bit 9 of the successive comparison register varies depending on the comparison result as follows.
• If V
< V
, then "1" is assigned to bit 9.
REF
IN
• If V
> V
, then "0" is assigned to bit 9.
REF
IN
2. Fixes bit 8 of the successive comparison register.
Sets bit 8 of the successive comparison register to "1", then compares V
Bit 8 of the successive comparison register varies depending on the comparison
result as follows:
• If V
< V
, then "1" is assigned to bit 8.
REF
IN
• If V
> V
, then "0" is assigned to bit 8.
REF
IN
3. Fixes bit 7 through bit 0 of the successive comparison register.
Carries out step 2 above on bit 7 through bit 0.
After bit 0 is fixed, the contents of the successive comparison register (conversion result) are trans-
mitted to A-D register i.
V
is generated based on the latest content of the successive comparison register. Table 2.31
REF
shows the relationship of the successive comparison register contents and V
how the successive comparison register and V
2.93 shows theoretical A-D conversion characteristics.
Table 2.33:
Relationship of successive comparison register contents and V
Successive approximation register: n
1 to 1023
Rev.1.00 Sep 24, 2003 Page 246 of 360
: [In this instance, the contents of the successive comparison register are
IN
0
) generated internally based on the contents
REF
) input from the analog input pin.
IN
REF
vary while A-D conversion is in progress. Figure
REF
V
REF
1024
A-D Converter
with V
.
IN
. Table 2.32 shows
REF
REF
V
(V)
REF
0
x n - V
REF
2048
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