Converting a SLC 150 program - Fine Timebase

[brstilson]

Converting a SLC 150 program to Micrologix 1400 and I see rungs like this

    708  873          907

+---] [--] [----------(CTU)--+

                        PR 0005

The 873 address has no associated OTE instruction. So I looked in the manual and it said this was a special timebase instruction that corresponds to 100 milliseconds. So, am I correct in assuming the above "Counter" is actually being used as a 500 millisecond timer? If so, the RTOs in the SLC 150 could specify times at the 0.1 second level, so why bother with something like this?

 

[TConnolly]

Chances are the original programmer was following the example on page 8.4 of the manual. As to why he didn't use a regular RTO we would need to see the program to make any kind of a guess.

 

[brstilson]

So I'm correct the rung I posted is, in effect, a 500 millisecond timer?

 

[TConnolly]

That is what it looks like. Take a look at how 907 is reset and how it is used elsewhere in the program to verify that.