The processor configuration of PLC-5 used for example is listed below. This configuration may differ for different applications.
1. An Industrial Computer of Allen-Bradley 1784-T45 is utilized.
2. The command of Data Monitor is utilized to arrange the table of sequencer.
3. Two modules of output in Rack 0, group of module 0 (O:000).
4. The DL20 is identified as follows:
• Time driven
• DC inputs
• scan = 4, debounce = 1
• High true logic
• Binary message/variable data
Figure below demonstrates how individual inputs can activate unique matching messages. If two or more inputs are correct at the similar time, the rung closest to the end of the ladder diagram has precedence and only that message is activated during this scan of program.
When no inputs are correct, the display clears since the 1st rung displayed always activates special message #1. If the application needs that the last message stays shown indefinitely, do not program the 1st rung. The message feature of DL20 Auto Clear has to be disabled for this operation type.
In this case, one rung is needed for every unique message to be activated. The DL20 observes 10 bits (D0-D9) on the port of parallel when a number of message is strobed in. If message data of binary is chosen, a unique message numbers range from 1 to 1022 is permitted. If message data of BCD is chosen, a unique message numbers range from 1 to 399 is permitted.
Activate special message no 1 to apparent the display if no other messages are being activated in an afterward rung. A stable 1 is saved in address N7:0.
Activates message number 20 if input B3:1 is right and if rungs 3 and 4 are not correct.
Activates message number 21 if input B3:2 is right and if rung 4 is not correct.
Activates message number 22 if input B3:3 is right.
This case gives an operation priority type. For instance, rung 4 on message 22 has priority over rung 3 on message 21 as the later rung (if right) will write over any earlier message number place into output word 0:000.
The instruction of CPT will get all 16 bits of the description source word and transfer it into the selected destination word. This command may also be alternated with a MVM (move with mask) instruction or MOV (move) instruction.