Analog Input
VSBC-8 Reference Manual
Reference
–
39
T
WO
’
S
C
OMPLEMENT
D
ATA
F
ORMAT
(±5V
AND
±10V O
NLY
)
The A/D converter translates applied analog voltages into 12-bit, two’s complement digital
words. The full analog input range is divided into 4096 steps. The output code (0000h) is
associated with a mid-range analog value of 0 Volts (ground).
The formulas for calculating analog or digital values are given by:
Digital =
Analog
Step
Analog = Step Digital
x
Where:
Analog = Applied voltage
Digital
= A/D Conversion Data
Step
= 0.004882813 Volts (0 to +10V Range)
0.002441406 Volts (0 to +5V Range)
Sample values are shown in the table below:
Table 21: Two’s Complement Data Format
±5V Input
Voltage
±10V Input
Voltage
Hex
Decimal
Comment
+5.000000
+10.000000
—
—
Out of range
+4.997559
+9.995117
07FFh
2047
Maximum positive voltage
+2.500000
+5.000000
0400h
1024
Positive half scale
+1.250000
+2.500000
0200h
512
Positive quarter scale
+0.002441
+0.004883
0001h
1
Positive 1 LSB
0.000000
0.000000
0000h
0
Zero (ground input)
–0.002441
–0.004883
FFFFh
–1
Negative 1 LSB
–1.250000
–2.500000
FE00h
–512
Negative quarter scale
–2.500000
–5.000000
FC00h
–1024
Negative half scale
–5.000000
–10.000000
F800h
–2048
Maximum negative voltage
