CHAPTER 10 A/D CONVERTER
Preliminary User’s Manual U16846EJ1V0UD
185
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.
Figure 10-3. Format of A/D Converter Mode Register (ADM)
144 s
Note 1
120 s
Note 1
96 s
72 s
60 s
48 s
ADCE
0
0
FR0
FR1
FR2
0
ADCS
A/D conversion operation control
Stops conversion operation
Enables conversion operation
ADCS
0
1
Conversion time selection
Note 1
288/f
X
240/f
X
192/f
X
144/f
X
120/f
X
96/f
X
Setting prohibited
FR2
0
0
0
1
1
1
Other than above
FR1
0
0
1
0
0
1
FR0
0
1
0
0
1
0
<0>
1
2
3
4
5
6
<7>
ADM
Address: FF28H After reset: 00H R/W
Symbol
µ
µ
µ
µ
µ
µ
34.3 s
28.6 s
22.9 s
17.2 s
14.3 s
11.5 s
Note 1
28.8 s
24.0 s
19.2 s
14.4 s
12.0 s
Note 1
9.6 s
Note 1
µ
µ
µ
µ
µ
µ
f
X
= 8.38 MHz f
X
= 10 MHz
18 s
15 s
12 s
Note 1
9 s
Note 1
7.5 s
Note 1
6 s
Note 1
µ
µ
µ
µ
µ
f
X
= 16 MHz
Boost reference voltage generator operation control
Note 2
Stops operation of reference voltage generator
Enables operation of reference voltage generator
ADCE
0
1
µ
µ
µ
µ
µ
µ
f
X
= 2 MHz
µ
Notes 1. Set so that the A/D conversion time is 14
µ
s or longer but less than 100
µ
s.
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
µ
s from operation
start to operation stabilization. Therefore, when ADCS is set to 1 after 14
µ
s or more has elapsed
from the time ADCE is set to 1, the conversion result at that time has priority over the first conversion
result.
