Slc 150 Scan Instruction 869

i AM CONVERTING A SLC 150 PROGRAM TO SLC500 BUT CAME ACROSS
AN INPUT LABLED SCAN WITH AN ADDRESS OF 869 I CAN'T FIND IT IN THE USER MANUAL SPECIAL INSTRUCTIONS STOP AT 868 IT LOOKS LIKE SOME SORT OF ONE SHOT HAS ANYONE HEARD OR THIS...THANKS I'M NEW TO THIS FORUM.BAP

Fast counters

Hello bab and welcome to the fourm.

Address 869 thru 873 are use as fine time base counter. They count the scan rate of the program.

For the SLC 100 the rates are:
869 = Scan rate
870 = 10
871 = 20
872 = 40
873 = 80

For the SLC 150 the rates are:
869 = Scan rate
870 = 10
871 = 20
872 = 50
873 = 100

These are usually place on line with counters.

How would that equate to a slc 500 program? ...bap

Would I replace the counter with a TON since SLC 500 has a finer time base? BAP

YES i would replace the counters with timers.

Sorry for the mispelled name.


Pat

Thanks Pat....BAP

The special registers were used for 'high speed timing', since the SLC 100/150 have a default of 0.1 second resolution. What they did was to provide dedicated bits that toggle at a fast rate, and then you would use a counter to essentially count the time, using these pulses. I also translated one recently, and the easy way to do it is to use a timer with a 0.01 base, and move on.
Now, if the programmer really intended to use the 869/870... for blinking a lite or other function, of course you could generate an equivalent bit with a time, or, perhaps use the S:4 register to save some work..(that's what I did).