Datasheet

CHAPTER 9 A/D CONVERTER ( μ PD78F920x ONLY)
User’s Manual U18172EJ3V0UD
162
Figure 9-3. Format of A/D Converter Mode Register (ADM)
Address: FF80H After reset: 00H R/W
Symbol <7> 6 5 4 3 2 1 <0>
ADM ADCS 0 FR2 FR1 FR0 0 0 ADCE
ADCS A/D conversion operation control
0 Stops conversion operation
1
Note 1
Starts conversion operation
fXP = 8 MHz fXP = 10 MHz FR2 FR1 FR0 Reference
Voltage
Range
Note 2
Sampling
Time
Note 3
Conversion
Time
Note 4
Sampling
Time
Note 3
Conversion
Time
Note 4
Sampling
Time
Note 3
Conversion
Time
Note 4
0 0 0 VDD ≥
4.5 V
12/fXP 36/fXP 1.5 μ s 4.5 μ s 1.2 μ s 3.6 μ s
1 0 0 VDD ≥
4.0 V
24/fXP 72/fXP 3.0 μ s 9.0 μ s 2.4 μ s 7.2 μ s
1 1 0 96/fXP 144/fXP 12.0 μ s 18.0 μ s 9.6 μ s 14.4 μ s
1 0 1 48/fXP 96/fXP 6.0 μ s 12.0 μ s 4.8 μ s 9.6 μ s
0 1 0 48/fXP 72/fXP 6.0 μ s 9.0 μ s 4.8 μ s 7.2 μ s
0 0 1
V
DD ≥
2.85 V
24/f
XP 48/fXP 3.0 μ s 6.0 μ s Setting
prohibited
Note 5
(2.4
μ s)
Setting
prohibited
Note 5
(4.8
μ s)
1 1 1 176/fXP 224/fXP 22.0 μ s 28.0 μ s 17.6 μ s 22.4 μ s
0 1 1
V
DD ≥
2.7 V
88/f
XP 112/fXP 11.0 μ s 14.0 μ s Setting
prohibited
Note 5
(8.8
μ s)
Setting
prohibited
Note 5
(11.2
μ s)
ADCE Comparator operation control
Note 6
0
Note 1
Stops operation of comparator
1 Enables operation of comparator
Remarks 1. fXP: Oscillation frequency of clock to peripheral hardware
2. The conversion time refers to the total of the sampling time and the time from successively
comparing with the sampling value until the conversion result is output.
Notes 1. Even when the ADCE = 0 (comparator operation stopped), the A/D conversion operation starts if
the ADCS is set to 1. However, the data of the first conversion is out of the guaranteed-value
range, so ignore it.
2. Be sure to set the FR2, FR1, and FR0, in accordance with the reference voltage so that Notes 2
and 3 below are satisfied.
Example When V
DD ≥ 2.7 V, fXP = 8 MHz
• The sampling time is 11.0
μ s or more and the A/D conversion time is 14.0 μ s or
more and 100 μ s or less.
• Set FR2, FR1, and FR0 = 0, 1, 1 or 1, 1, 1.