RSLogix Emulator 500 Mistake

[Narlin]

RSLogix Emulate 500: FYI

This 1 line, 2 instruction, ladder code causes a controller fault in the emulator, but always runs perfectly on a Micrologix machine.

---LES N7:11 15 OTL B3:1/[N7:11]

When the emulator tries to compile this code, and N7:11 is >15, then it faults the emulator. That is wrong. The rule is “If the rung evaluates as FALSE, then an OTL instruction does not execute”.

If you load the instruction into the emulator with N7:11 < 15, then it compiles, but when N7:11 becomes >15, it faults.

In a real Micrologix machine, it always runs well.


narlin

 

[bernie_carlton]

It may depend on the stored value of N7:11 at the time of the compile and pre-scan. Regardless of the logic the pre-scan attempts to evaluate all instructions. Even previous versions of hardware SLC processors' firmware would fault if the index at the time of the pre-scan was larger than allowed even if later scans would have modified the index to be valid when the instruction would be executed as true. Later versions on compile just yield a warning. The emulator is probably based on an early firmware model.

 

[Narlin]

Bernie, you are correct about the emulator prescan checking all instructions and thus needing a valid value at prescan. So…give it a valid value to get it compiled and it will run. Then go online with the emulator and change the value to >15. Then the emulator faults even though it was already running. To me, this means that the emulator is not working right.

 

[bernie_carlton]

So the current hardware CPU must be able to interpret B3:1/[>15] value as an offset into the next word (I assume - I can't test this right now) while the emulator (again a guess that it's derived from an earlier firmware) doesn't. It's not a 'fault' as much as it's basis is not up to the latest firmare for the device it is emulating. Just semantics.

 

[James Mcquade]

Narlin,

what micrologix are you using?
what firmware?

i can get this to run in my emulator, i will try what the others have said.

regards,
james

 

[Narlin]

My emulator is Rev 6.00.00.07 (CPR 9). I just downloaded it about a week ago. It should be the latest. The micrologix is an 1100 and a 1400. Both of those work fine.