State Logic exposure

Hi all,

Back in 1995 I was exposed to GE Fanuc’s State Logic as the client recommended solution to two batching projects; one using the 9030 CSE and the other using two 9070 CSEs. It took a while to get used to the idiosyncrasies of the language, but I found it to be easy to debug and troubleshoot. Fast forward to today. GE now has their PAC CPUs released and uses Machine Edition as the programming tool. They migrated the State Logic editor to Machine Edition, but only as a 16bit implementation, and not supported in the PAC arena.

My two clients needed to upgrade their systems. The one with the 9070 CPUs has 110 Genius I/O blocks in the plant and would be very expensive to change platforms. I chose the RX7i system for them and the RX3i for the 9030 replacement. Along with this, I developed a ladder logic version of the State Logic engine, having worked with it for over 10 years.

My question to you all is: Have any of you worked with or come across State Logic systems? What did you think of the implementation? Do the end users have any support concerns since GE seems to have abandoned this language? I appreciate any and all input.

Clarify for the ignorant please. what is state logic?

Read this thread.
http://gefanuc.bnsi.net/eforum/showthread.php?s=&threadid=5992&highlight=state+logic

This may give you an idea; http://www.patchn.com/plc_sequ.pdf

I believe some PLCs refer to it as Stage programming. It is basically just doing things in a sequential order similar to using a DRUM type instruction.

As is noted there are case where actual state logic differs from ladder logic. In my examples above it explains using state but being converted to use ladder logic.

rsdoran said:

This may give you an idea; http://www.patchn.com/plc_sequ.pdf

I believe some PLCs refer to it as Stage programming. It is basically just doing things in a sequential order similar to using a DRUM type instruction.

Click to expand...

The GE Fanuc State Logic programming is a little more than this. Most all PLC programming is sequential as most all machines and processes are sequential. A DRUM instruction is a 'special purpose' sequence function. You could do any machine or process with several DRUM switches (in fact before PLCs we did). The GE Fanuc State Engine is a software device or tool-set that made development and troubleshooting very easy. The problem with it is that it takes a different way of development of both the control tasks and the diagnostic tasks to take advantage of these ease of use tools. Most ladder logic programmers who tried this never took the time to learn how to use these tools but rather tried to make them work like ladder. This was very inefficient. Because it was not readilly embraced by the public it got left behind.

Simple State Logic Example

[font=&quot]Task: Tank_Fill
!This is the startup state
State: Init
If TANK_LEVEL < 20 THEN
Goto StartFill

!This state does the actual tank fill
State: StartFill
If TANK_LEVEL < 95
Turn_On FILL_PUMP
Open FILL_VALVE
If TANK_LEVEL >= 95 OR FLOAT_SWITCH is ON THEN
Goto Init


TANK_LEVEL is defined as an AI
FILL_PUMP and FILL_VALVE are defined as DO's
FLOAT_SWITCH is defined as a DI

Turn_On, Open, Goto are Keywords

The above English text is read by a compiler and converted into a ladder logic equivalent, that the user cannot edit, and downloaded to the controller
[/font]

[font=&quot]There could be 32 tasks and a maximum of 32 states in each task. Each task (program file) can only be in one state each scan. If a task is stuck in a state it is a simple matter to see what condition(s) prevent a state transfer.
[/font]

There could be 32 tasks and a maximum of 32 states in each task. Each task (program file) can only be in one state each scan. If a task is stuck in a state it is a simple matter to see what condition(s) prevent a state transfer.

Click to expand...

This can also be known as step programming, or as rsdoran pointed out, sequential order, otherwise know as a sequential function chart. Many PLC's can implement this method, either by using graphical software such as graphcet, developing your own set of SFC's, and then implementing them into ladder.

This method of programming is robust and easy to diagnose, as stated,

If a task is stuck in a state it is a simple matter to see what condition(s) prevent a state transfer

Click to expand...

Can make fault finding, and even commissioning sometimes much easier.

Thanks guys. I would't call myself an expert, but I have the basic idea now.