Registers Used In A/D Converter - NEC MuPD78F0132H User Manual

12.3 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 <7>
ADM ADCS
ADCS
0
1
FR2
0
0
0
1
1
1
ADCE
0
1
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.
Remark f : High-speed system clock oscillation frequency
X
CHAPTER 12 A/D CONVERTER
Figure 12-3. Format of A/D Converter Mode Register (ADM)
After reset: 00H R/W
6 5
0 FR2
Stops conversion operation
Enables conversion operation
FR1 FR0
288/f
0 0
240/f
0 1
192/f
1 0
144/f
0 0
120/f
0 1
96/f
1 0
Other than above Setting prohibited
Boost reference voltage generator operation control
Stops operation of reference voltage generator
Enables operation of reference voltage generator
User's Manual U16899EJ2V0UD
4 3 2
FR1 FR0 0
A/D conversion operation control
Conversion time selection
f = 2 MHz f = 8.38 MHz f
X X
µ
µ
Note 1
144 s 34.3 s
X
µ
µ
Note 1
120 s 28.6 s
X
µ
µ
96 s
22.9 s
X
µ µ
72 s 17.2 s
X
µ µ
60 s 14.3 s
X
µ
µ
Note 1
48 s
11.5 s
X
µ
s or longer but less than 100
1 <0>
0 ADCE
Note 1
f = 16 MHz
= 10 MHz
X
X
µ
µ
28.8 s 18 s
µ
µ
24.0 s 15 s
µ µ
Note 1
12 s
19.2 s
µ
µ
Note 1
14.4 s 9 s
µ µ
Note 1 Note 1
12.0 s 7.5 s
µ µ
Note 1 Note 1
9.6 s 6 s
Note 2
µ
s.
µ
s from operation
µ
s or more has elapsed
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