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Analog I/O Units Section 7-4
Creating a Ladder
Program
I/O Allocation
Two input words and one output word are allocated to the Analog I/O Unit
starting from the next word following the last allocated word on the CPU Unit
or previous Expansion Unit or Expansion I/O Unit.
Writing the Range Code
Write the range code to word n+1. A/D or D/A conversion begins when the
range code is transferred from the CPU Unit to the Analog I/O Unit. There are
five range codes, 000 to 100, that combine the analog input 1 and 2 and ana-
log output signal ranges, as shown below.
Example
The following instructions set analog input 0 to 4 to 20 mA, analog input 1 to 0
to 10 V, and the analog output to −10 to 10 V.
• The Analog I/O Unit will not start converting analog I/O values until the
range code has been written. Until conversion starts, inputs will be 0000,
and 0 V or 0 mA will be output.
• After the range code has been set, 0 V or 0 mA will be output for the 0 to
10-V, −10 to 10-V, or 0 to 20-mA ranges, and 1 V or 4 mA will be output for
the 1 to 5-V and 4 to 20-mA ranges until a convertible value has been
written to the output word.
• Once the range code has been set, it is not possible to change the setting
while power is being supplied to the CPU Unit. To change the I/O range,
turn the CPU Unit OFF then ON again.
Range
code
Analog input 0 signal
range
Analog input 1 signal
range
Analog output signal
range
000 −10 to 10 V −10 to 10 V −10 to 10 V
001 0 to 10 V 0 to 10 V 0 to 10 V
010 1 to 5 V/4 to 20 mA 1 to 5 V/4 to 20 mA 1 to 5 V
011 0 to 5 V/0 to 20 mA 0 to 5 V/0 to 20 mA 0 to 20 mA
100 --- --- 4 to 20 mA
Analog I/O Unit
Word m+1
Word m+2
32 inputs
16 outputs
Word n+1
n+1
15
1 0 0 0 0 0 0
8 7 6 5 4 3 2 1
0
Analog
output
Analog
input 1
Analog
input 0
MOV(021)
#800A
n+1
First Cycle Flag
A200.11
Analog input 0: 4 to 20 mA
Analog input 1: 0 to 10 V
Analog output: −10 to 10 V
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