AB scan sequence

[mordred]

OK understand that thus far so how do you eliminate the chances if you require the same output control onto two different sub routines for example would you copy the states into a memeory location for example and only call the adderess when you desire to poll the state?

 

[kamenges]

The generally accepted way of doing this is to have the controlling logic drive different internal bits in each of the routines. Then use these bits in parallel to drive the desired output.

Keith

 

[mordred]

ok simple enough thanks Kaminges its useful to learn stuff on those processors you've never used just in case

 

[Ron Beaufort]

just to answer a specific question ...

to plc noob ...

so if you did for some reason have an output that you wanted to turn on and then off during the same scan . it could be possible by implementing the correct spacing of the outputs in the program and the correct adjustment of the rpi . is this correct ?

let's ignore for a minute the obvious question: "Why would you want to do such a thing?" - and just give you a straight answer ...

no ... that's not the way it would be done ... too much would depend on the processor's scan speed, the addition of new program rungs, the alignment of Jupiter with Mars, etc. ...

if you REALLY do want to see the output device in the field change states between one rung and another, you'd insert a new rung BETWEEN the conflicting control rungs ... that new rung would have an IOT (Immediate Output) instruction on it ...

think of this as an extra "special delivery" command - which will send the output status FROM the data table bits TO the output module INDEPENDENTLY of the RPI - and INDEPENDENTLY of the processor's normal "end of scan" transmission ...

in human terms: "Send this stuff NOW!" ...