4-4
VL-1225/6 Analog Input/Output Board
Input Data Representation
The format of the data read from the board varies depending on the input range and the data format that
is selected. Each of the data formats is discussed below.
Input Binary Format (10-Bit Resolution)
Binary format is used only with the unipolar 0 to +10V input range. 10-bit binary format divides the full
10 Volt analog input range into 1024 steps of 9.77 mV each. The code 0000H is associated with an analog
input voltage of 0 Volts (ground). The largest code (03FFH) describes the highest voltage, i.e., +9.9902
Volts. All codes are considered positive. The upper six bits of the Data High register are all zeros.
The formulas for calculating analog or binary digital values are given by:
Analog
Digital =
————
Analog = Step
×
Digital
Step
Where:
Analog
= Applied voltage
Digital
= A/D Conversion Data
Step
= 0.00976563
Sample values are shown in the table below:
Input
Data
Data
Voltage
(Hex)
(Decimal)
Comment
+10.0000
—
—
Out of range
+9.9902
03FF
1023
Maximum voltage
+5.0000
0200
512
Half scale
+2.5000
0100
256
Quarter scale
+1.2500
0080
128
Eighth scale
+0.00977
0001
1
1 LSB
0.0000
0000
0
Zero (ground input)
Figure 4-2. Binary Data Format (10-Bit Resolution)
Registers – Analog Input Registers
