Question

Hey

I´m stille new to programming AB. I have a question regarding outputs and bits. What does (L) or (U) means. Latch or unlatch, but what is that

A latch is an output instruction that comes on and stays on until it is unlatched. An ordinary output will come on and stay on until the rung goes false. With a latch, even if the rung goes false, the output remains on until the unlatch instruction turns it off.


Hope that helps

Marc

Marc said:

A latch is an output instruction that comes on and stays on until it is unlatched. An ordinary output will come on and stay on until the rung goes false. With a latch, even if the rung goes false, the output remains on until the unlatch instruction turns it off.


Hope that helps

Marc

Click to expand...

Latched memory bits will retain their state during a shutdown (on/off) or if the program is stopped and restarted; real outputs will be reset to off before the first scan.

Thanks guys.....

How the OTL and OTU are displayed can be confusing to some folks. The intructions are higlighted (or not) depending on the value of the bit, not the condition of the instruction. I've had new techs ask, "Why is this output on, even through the input instruction is false?"

See the attached picture. Neither of the rungs make sense if you think the green highlight describes the instruction's condition. They're thinking it's ON or TRUE, when in fact the green highlight is telling you that B3/1 is equal to 1. Press button #1 to make B3/1 = 1. Press button #2 to make B3/1 = 0.

Good point Mark


I forgot to mention that, sort of comes as second nature after you know what to look for but it sure can mess up someone who isn't aware of how a OTL OTU is displayed.

marc