4-12
VL-1225/6 Analog Input/Output Board
Output Two’s Complement Format
Two’s Complement format is used with the ±5V or the ±10V output ranges. It divides the full bipolar analog
output range into 256 steps. The code 00H produces an analog output of 0 Volts. Positive digital values
produce positive analog output voltages, and negative digital values produce negative analog output
voltages. Two’s complement format is the most common format for expressing bipolar analogs.
The formulas for calculating analog or two’s complement digital values are given by:
Analog
Digital =
————
Analog = Step
×
Digital
Step
Where:
Analog
= Applied voltage
Digital
= D/A Conversion Data
Step
= 0.078125
(±10V Range)
0.0390625
(±5V Range)
Sample values are shown in the table below:
±5V Output
±10V Output
Data
Data
Voltage
Voltage
(Hex)
(Decimal)
Comment
+5.0000
+10.0000
—
—
Out of range
+4.9609
+9.9219
7F
127
Maximum positive voltage
+2.5000
+5.0000
40
64
Positive half scale
+1.2500
+2.5000
20
32
Positive quarter scale
+0.03906
+0.07813
01
1
Positive 1 LSB
0.0000
+0.0000
00
0
Zero Volts
– 0.03906
– 0.07813
FF
– 1
Negative 1 LSB
– 1.2500
– 2.5000
E0
– 32
Negative quarter scale
– 2.5000
– 5.0000
C0
– 64
Negative half scale
– 5.0000
– 10.0000
80
– 128
Maximum negative voltage
Figure 4-10. Two’s Complement Format
Registers – Analog Output Registers
Содержание STD32 VL-1225
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