Help with Instruction in RSLogix 500

[diat150]

Can someone explain to me the purpose of this IOM instruction? N10:8 is fed from a PID and as you can see, when the PID Control bit is enabled, the N10:8 value gets moved to the output. We are seeing the output swing from 0 to 31290 even though the PID is in manual and set to 100%(31290). This IOM instruction is the only thing I can see causing this.

 

[MikeyN]

The IOM as it sits in your program is being used to stop the scan, energize all set bits in O:9.1 (or in this case pass 7490 to whatever device you are connected to), and then resume scanning. The mask of FFFFh means that all bits are eligible to be energized, ie there is no masking happening.

On a side note, are you online when you are viewing this? In my editor, the rung numbers and bus bars are green when I am online. I am guilty of doing this more often than I would like to admit...

 

[Operaghost]

Normally the Output data is sent to the physical output module only at the end of the scan.

The IOM tells the controller to stop, update that address on the physical module, then resume scanning.

It is very common to see this instruction used, sometimes the IIM is also used, inside of a Selectable Timed Interrupt (STI) routine which is where we usually put a PID instruction.

Not unusual to see:

IIM
PID
IOM

In that order


OG