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CHAPTER 14 A/D CONVERTER
User’s Manual U16890EJ1V0UD
415
(1) A/D converter mode register (ADM)
This register sets the conversion time of the analog input signal to be converted into a digital signal as well as
conversion start and stop.
The ADM register can be read or written in 8-bit or 1-bit units.
After reset, ADM is cleared to 00H.
ADCS
ADCS
0
1
Conversion operation stopped
Conversion operation enabled
Control of A/D conversion operation
ADM
0
FR2
FR1
FR0
0
0
ADCS2
After reset: 00H R/W Address: FFFFF200H
FR2
0
0
0
0
1
1
1
1
FR1
0
0
1
1
0
0
1
1
FR0
0
1
0
1
0
1
0
1
288/f
XX
240/f
XX
192/f
XX
Setting prohibited
144/f
XX
120/f
XX
96/f
XX
Setting prohibited
14.4 s
Setting prohibited
Setting prohibited
Setting prohibited
Setting prohibited
Setting prohibited
Setting prohibited
Setting prohibited
18.0 s
15.0 s
Setting prohibited
Setting prohibited
Setting prohibited
Setting prohibited
Setting prohibited
Setting prohibited
Conversion time
Note 1
Selection of conversion time
20 MHz
16 MHz
28.8 s
24.0 s
19.2 s
Setting prohibited
14.4 s
Setting prohibited
Setting prohibited
Setting prohibited
10 MHz
f
XX
ADCS2
0
1
Reference voltage generator operation stopped
Reference voltage generator operation stopped
Control of reference voltage generator for boosting operation
Note 2
< >
< >
Notes 1.
Setting the conversion time (time actually required for A/D conversion) as follows is prohibited.
AV
REF0
≥
4.0 V: Less than 14
μ
s
AV
REF0
< 4.0 V: Less than 17
μ
s
2.
The operation of the reference voltage generator for boosting is controlled by the ADCS2 bit and it
takes 17
μ
s (14
μ
s when AV
REF0
≥
4.0 V) after operation is started until it is stabilized. Therefore the
ADCS bit is set to 1 (A/D conversion is started) at least 17
μ
s (14
μ
s when AV
REF0
≥
4.0 V) after if
the ADCS2 bit was set to 1 (reference voltage generator for boosting is on), the first conversion
result is valid.
Cautions 1. Be sure to clear bits 6, 2, and 1 to 0.
2. Changing bits FR0 to FR2 while the ADCS bit = 1 is prohibited (write access to the ADM
register is enabled and rewriting of bits FR0 to FR2 is prohibited).
3. When the main clock is stopped and the CPU is operating on the subclock, do not access
the ADM register using an access method that causes a wait. For details, refer to 3.4.8 (2).
Remark
f
XX
: Main clock frequency