
229
CHAPTER 13 A/D CONVERTER
User
’
s Manual U14260EJ3V1UD
Figure 13-3. Format of A/D Converter Mode Register 0 (ADM0)
Address: FF80H After reset: 00H R/W
Symbol
7
6
5
4
3
2
1
0
ADM0
ADCS0
TRG0
FR02
FR01
FR00
EGA01
EGA00
ADCE0
ADCS0
A/D conversion operation control
0
Stop conversion operation.
1
Enable conversion operation.
TRG0
Software start/hardware start selection
0
Software start
1
Hardware start
FR02
FR01
FR00
Conversion time selection
Note 1
f
X
= 8.38 MHz
f
X
= 12 MHz
Note 2
0
0
0
144/f
X
17.1
μ
s
12.0
μ
s
0
0
1
120/f
X
14.3
μ
s
10.0
μ
s
Note 4
0
1
0
96/f
X
11.4
μ
s
Note 3
8.0
μ
s
Note 4
1
0
0
72/f
X
8.5
μ
s
Note 3
6.0
μ
s
Note 4
1
0
1
60/f
X
7.1
μ
s
Note 3
5.0
μ
s
Note 4
1
1
0
48/f
X
5.7
μ
s
Note 3
4.0
μ
s
Note 4
Other than above
Setting prohibited
EGA01
EGA00
Edge specification of external trigger signal
0
0
No edge detection
0
1
Falling edge detection
1
0
Rising edge detection
1
1
Both falling and rising edge detection
ADCE0
Boost reference voltage generator for A/D converter circuit control
Note 5
0
Stop operation of boost reference voltage generator.
1
Enable operation of boost reference voltage generator.
Notes 1.
Set the A/D conversion time as follows.
When operated at f
X
= 12 MHz (V
DD
= 4.5 to 5.5 V):
When operated at f
X
= 8.38 MHz (V
DD
= 4.0 to 5.5 V): 14
μ
s or more
2.
Expanded-specification products of
μ
PD780078 Subseries only.
3.
Setting is prohibited because the A/D conversion time is less than 14
μ
s.
4.
Setting is prohibited because the A/D conversion time is less than 12
μ
s.
5.
The on-chip booster is provided to realize low-voltage operation. The circuit that generates the
reference voltage for boosting is controlled by ADCE0 and it takes 14
μ
s for operation to stabilize after
it is started. Therefore, by waiting for at least 14
μ
s to elapse before setting ADCS0 to 1 after ADCE0
has been set to 1, the conversion results are valid from the first result.
12
μ
s or more
Remark
f
X
: Main system clock oscillation frequency