3-1
Section
Analog I/O Units
173
For analog outputs it is possible to use both voltage outputs and current outputs
at the same time, but the total current output must not exceed 21 mA.
Note
1. Use 2-core shielded twisted-pair cables.
2. Wire away from power lines (AC power supply wires, power lines, etc.)
3. When an input is not being used, short V IN and I IN to the COM terminal.
4. Use crimp terminals. (Tighten terminals to a torque of 0.5 N
⋅
m.)
5. When using current inputs, short V IN to I IN.
6. When there is noise in the power supply line, install a noise filter on the input
section and the Power Supply Unit.
Ladder Program
Specifying the Range Code
Specify the I/O signal range by writing the range code to the Analog I/O Unit’s
output word from the ladder program in the first cycle of program execution. The
Analog I/O Unit will start to convert analog I/O values once the range code has
been specified. (Refer to page 170.)
Write the range code to the Analog I/O Unit’s output word in the first cycle of op-
eration; the Analog I/O Unit’s output word is “n+1” when “n” is the last word allo-
cated to the CPU Unit, or previous Expansion Unit or Expansion I/O Unit in the
configuration.
Reading Converted Analog Input Values
A ladder program can be used to read the memory area where the converted
values are stored. Values are output to the next two words (m + 1, m + 2) follow-
ing the last input word (m) allocated to the CPU Unit, or previous Expansion Unit
or Expansion I/O Unit.
(m + 1)
(m + 2)
Analog input 1
Open-circuit
Detection Flag
0: Normal
1: Open-circuit
Analog input 1 conversion value (Hex: 00 to FF)
Analog input 2
Open-circuit
Detection Flag
0: Normal
1: Open-circuit
Analog input 2 conversion value (Hex: 00 to FF)
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Note
The Open-circuit Detection Flag is turned ON when the input signal range is set
to 1 to 5 V or 4 to 20 mA and the input signal falls below 1 V or 4 mA. (Open cir-
cuits are not detected when the input signal range is set to 0 to 10 V.)