Page 244 - Programmable Logic Controllers, Fifth Edition - Mobile version

• The MOV instruction is used to move the data from
the thumbwheel switch input to the LED display
output.
• Setting of the thumbwheel switch is compared to
the reference number 1208 stored in source B by the
EQU instruction.
• Pilot light output PL is energized whenever the
BCD
LED input switch S1 is true (closed) and the value of the
display board output module
Bit thumbwheel switch is equal to 1208.
BCD address
Decimal Input and output modules can be addressed either at
0
0 0 the bit level or at the word level. Analog modules con-
1s units 0 1 2 vert analog signals to 16-bit digital signals (input) or
1
3 16-bit digital signals to analog values (output). An analog
I/O will allow monitoring and control of analog voltages
0 and currents. Figure 10-41 illustrates how an analog input
0 4
10s units 1 5 6 interface operates. The operation of this input module can
0 be summarized as follows:
7
• The analog input module contains the circuitry nec-
1 essary to accept analog voltage or current signals
1 8 9
100s units 0 10 from field devices.
0
11 • The input signal is converted from an analog to a
digital value by an analog-to-digital (A/D) converter
0 circuit.
1 12
1000s units 0 13 • The conversion value, which is proportional to the
14
0
15 analog signal, is passed through the controller’s
data bus and stored in a specific register or word
L1 location in memory for later use by the control
L2 program.
An analog output interface module receives numerical
Figure 10-39 BCD output interface module connected to
a seven-segment LED display board. data from the processor; these data are then translated into
Source: Photo courtesy Omron Industrial Automation, www.ia.omron.com. a proportional voltage or current to control an analog field

Inputs Ladder logic program Outputs
L1 L2
MOV
MOVE
S1 Source TWS PL
Destination LED
1
2 S1 PL
TWS EQU
3 EQUAL
(All 16 bits) Source A TWS LED
4 (All 16 bits)
Source B 1208h
Thumbwheel switch
LED display
1 2 0 8 12 08

Figure 10-40 Monitoring the setting of a thumbwheel switch.

Data Manipulation Instructions Chapter 10 225

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