Hard Coding TON s

[zach_zachary1@yahoo.com 1]

I am relatively new to programing.  In one of my plants programs the programmers use an MOV to hard code the TON accumulator.  What is the advantage of this?

 

 

[panic mode 246]

it fixes value so it cannot be changed acidentaly.

also it is a way to use timer in structured text..

[b_carlton 61]

Notice that he wrote about MOVing a value to the ACCUMULATOR.

I've only seen this described once in creating a more accurate time source. With a preset of, let's say, 1 minute then, on the DN bit the expected preset was subtracted from the accumulator leaving whatever small amount over the preset had been loaded in evaluating the timer instruction. Thus the time between DN bits was,on the average, more accurate than just resetting the timer using a NC contact of the DN bit in the enable rung.

[Mickey 71]

I have seen this, to give a certain  something time to happen. If that certain something happens before the timer times out then why wait. Write to the .ACC and make the timer time out.

Waiting for message instruction(s) to complete or give them time to complete is a good example.

Edited 20 Mar 2016 by Mickey