UPD17073 NEC, UPD17073 Datasheet - Page 109

• Manufacturer Part Number: UPD17073
• Description: 4-BIT SINGLE-CHIP MICROCONTROLLER WITH HARDWARE FOR DIGITAL TUNING SYSTEM
• Manufacturer: NEC

13.7.2 Successive comparison by means of binary search
digital signals.
desirable because of the relations with the other programs.
(1) Concept of binary search
The A/D converter can compare only one reference voltage at a time.
Consequently, successive comparison must be executed through program in order to convert input voltages into
If the processing time of the successive comparison program is different depending on the input voltage, it is not
Therefore, the binary search method described in (1) through (3) below is useful.
Compare voltage
The following figure illustrates the concept of binary search.
First, the reference voltage is set to 1/2V
4V
Similarly, comparison is performed in sequence from 1/8V
has been executed six times, 1/64V
DD
is applied; if the result is False (low level), a voltage of 1/4V
( V
DD
)
First
1/2
1
0
H
L
Second
3/4
1/4
DD
H
L
H
L
is subtracted, and the comparison ends.
DD
. If the result of comparison is True (high level), a voltage of 1/
Third
7/8
5/8
3/8
1/8
H
L
H
L
H
L
H
L
DD
Fourth
15/16
13/16
11/16
9/16
7/16
5/16
3/16
1/16
to 1/16V
DD
L
L
L
L
L
L
L
L
DD
is subtracted for comparison.
. If the result is False after comparison
1
15/16
14/16
13/16
12/16
11/16
10/16
9/16
8/16
7/16
6/16
5/16
4/16
3/16
2/16
1/16
0/16
Subtract 1/16 if false
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