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10.3 Registers Used in A/D Converter
The A/D converter uses the following five registers.
• A/D converter mode register (ADM)
• Analog input channel specification register (ADS)
• A/D conversion result register (ADCR)
• Power-fail comparison mode register (PFM)
• Power-fail comparison threshold register (PFT)
(1) A/D converter mode register (ADM)
This register sets the conversion time for analog input to be A/D converted, and starts/stops conversion.
ADM can be set by a 1-bit or 8-bit memory manipulation instruction.
RESET input clears this register to 00H.
Address: FF28H
Symbol
ADM
Notes 1.
Set so that the A/D conversion time is 14
2.
A booster circuit is incorporated to realize low-voltage operation. The operation of the circuit that
generates the reference voltage for boosting is controlled by ADCE, and it takes 14
start to operation stabilization. Therefore, when ADCS is set to 1 after 14
from the time ADCE is set to 1, the conversion result at that time has priority over the first conversion
result.
CHAPTER 10 A/D CONVERTER
Figure 10-3. Format of A/D Converter Mode Register (ADM)
After reset: 00H
<7>
6
5
ADCS
0
FR2
ADCS
A/D conversion operation control
0
Stops conversion operation
1
Enables conversion operation
FR2
FR1
FR0
0
0
0
0
0
1
0
1
0
1
0
0
1
0
1
1
1
0
Other than above
ADCE
Boost reference voltage generator operation control
0
Stops operation of reference voltage generator
1
Enables operation of reference voltage generator
Preliminary User's Manual U16846EJ1V0UD
R/W
4
3
2
FR1
FR0
0
Conversion time selection
f
= 2 MHz
f
= 8.38 MHz f
X
X
X
µ
µ
Note 1
288/f
144 s
34.3 s
28.8 s
X
µ
µ
Note 1
240/f
120 s
28.6 s
24.0 s
X
µ
µ
192/f
96 s
22.9 s
19.2 s
X
µ
µ
144/f
72 s
17.2 s
14.4 s
X
µ
µ
120/f
60 s
14.3 s
12.0 s
X
µ
µ
Note 1
96/f
48 s
11.5 s
9.6 s
X
Setting prohibited
µ
s or longer but less than 100
1
<0>
0
ADCE
Note 1
= 10 MHz
f
= 16 MHz
X
µ
µ
18 s
µ
µ
15 s
µ
µ
Note 1
12 s
µ
µ
Note 1
9 s
µ
µ
Note 1
Note 1
7.5 s
µ
µ
Note 1
Note 1
6 s
Note 2
µ
s.
µ
s from operation
µ
s or more has elapsed
185
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