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I am using Allen-Bradley plc with RSLogix 500 as ladder logic software. For forcing any Digital XIC/XIO (i.e, DI/DO) on any rung to ON/OFF, i have to use 'FORCE ON or FORCE OFF' function.

but when i check the Data table, i am able to change the state of that DI/DO by using 'TOGGLE BIT' functions also,as i do for forcing any 'BIT (eg-B9:0/1)'ON/OFF. if i FORCE ON any D/O and then change it's binary state by using TOGGLE BIT,what will be the effect on my actual output.

can some one clear me about what's the difference in using 'TOGGLE BIT' and 'FORCE ON/OFF'function.

Forcing only works for digital inputs and outputs, and set the state to ON or OFF no matter what is happening in your logic while Toggle will change the state of any bit/bool (I/O or internal) but the logic will still be able to change the state as processed.

Toggle bit: Output bit is switched momentarily from its current state to the complementary state and then the bit is back to the current state.

FORCE ON: Bit is forced ON (1) condition till the time forcing is removed.

FORCED OFF: Bit is forced OFF (0) condition till the time forcing is removed.

PLC has force tables.. When you force an Input address, you are 'or'ing' with the normal Input scan and affecting the data tale.. when you force an output you are writing to the output scan and not the data table so the output address in the data table is not affected by the force

The output data table bit responds to the logic in the PLC always!!

I/O needs forcing. Data table bits you can toggle

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