The illustrates below is the Individual Inputs PLC-2 for Triggering Messages
If two (2) or more inputs are correct at the similar time, the rung bordering to the ladder diagram end has right of way and only this message is activated during the scan of program. When no inputs are correct, the display apparent since the first rung displayed always activates special message #1 if nothing of the rungs after it are correct. Special message #1 clears the display. If the application needs that the final message showed remains shown for an indefinite period, do not program the 1st rung in this case. The message feature of DL20 Auto Clear must be disabled for this operation type.
In this case, one rung is needed for every unique message activated. The DL20 observes 10 bits that is D0 to D9 on the port of parallel when a number of messages are strobe in. The message numbers range from 1-1022 is permitted if binary is selected. If BCD is chosen, a message numbers range from 1-399 is permitted.
Rung Descriptions
Rung 1
Activates special message #1 to apparent the display, if no other messages are being activated in an afterward rung. A stable 1 is saved in address 057.
Rung 2
Activate message 20 if input 112:00 is correct and if rungs 3 and 4 are not correct.
Rung 3
Activate message 21 if input 112:01 is correct and if rung 4 is not correct.
Rung 4
Activate message 22 if input 112:02 is correct.
The ladder diagram gives a priority of type operation. For instance, rung 4 on message 22 has priority over rung 3 on message 21 because the afterward rung will write over any earlier message number located into word 010, if enabled. Words 057 on bits 14 and 15 of through 062 have to be set. The numbers of message saved in these words are entered while programming the instructions of GET. After that, bit 14 and 15 are set with the command of “SEARCH 53”. Bits 14 and 15 communicate to the strobe terminals MS0 and MS1 on the DL20 with PLC-2.
Get and Put Instructions
The instruction of GET moves 16 bits of the selected word and puts it in the PUT instructions selected word. Though, only the lowest 12 bits (<12 bits) are showed on the industrial terminal in BCD (Binary-Coded Decimal) form. The instructions of GET as shown in illustrates above have two added bits set which are not noticeable on the terminal ladder diagram industry. Those are bits 14 and 15. These outputs are linked to the strobe bits of MS0 and MS1 on the parallel port of DL20.