CHAPTER 10 8-BIT A/D CONVERTER (
µµµµ
PD789426 AND 789446 SUBSERIES)
User’s Manual U15075EJ1V0UM00
186
10.3 8-Bit A/D Converter Control Registers
The 8-bit A/D converter is controlled by the following two registers.
• A/D converter mode register 0 (ADM0)
• Analog input channel specification register 0 (ADS0)
(1)
A/D converter mode register 0 (ADM0)
ADM0 specifies the conversion time for analog inputs. It also specifies whether to enable conversion.
ADM0 is set with a 1-bit or 8-bit memory manipulation instruction.
RESET input sets ADM0 to 00H.
Figure 10-2. Format of A/D Converter Mode Register 0
A/D conversion control
ADCS0
0
1
A/D conversion time selection
Note 1
FR02
0
0
0
1
1
1
144/f
X
120/f
X
96/f
X
72/f
X
60/f
X
48/f
X
FR01
0
0
1
0
0
1
(28.8 s)
(24 s)
(19.2 s)
(14.4 s)
(Setting prohibited
Note 2
)
(Setting prohibited
Note 2
)
µ
µ
µ
FR00
0
1
0
0
1
0
Other than above
Conversion disabled
Conversion enabled
Setting prohibited
µ
ADCS0
0
FR02
FR01
FR00
0
0
0
ADM0
<7>
6
5
4
Symbol
Address
After reset
R/W
FF80H
00H
R/W
3
2
1
0
Notes 1. The specifications of FR02, FR01, and FR00 must be such that the A/D conversion time is at
least 14
µ
s.
2. These bit combinations must not be used, as the A/D conversion time will fall below 14
µ
s.
Cautions 1. Bits 0 to 2 and 6 must be set to 0.
2. The result of conversion performed immediately after setting ADCS0 is undefined.
3. The conversion result may be undefined after clearing ADCS0.
Remarks 1. f
X
: Main system clock oscillation frequency
2. The parenthesized values apply to operation at f
X
= 5.0 MHz.
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