15M control, PLC diagnostic F and G contacts???

[steve-o]

Hi,

Newbie alert!!!

More of a curiosity question rather than a problem I need to resolve.

Just wondered if any of you chaps knew what the F and G contacts relate to in the PLC diagnostics on the 15M control.

I only ask as I needed to find the output for an F contact so I could see what was switching it on and couldn't find the output???

Any ideas???

Cheers.
Steve.

[Al_The_Man]

Steve, the Fanuc has two processors, the CNC and the PMC, the CNC looks after processing the part program together with the servo control, the PMC operates the Machine functions such as M,S & T codes and the Input/Output functions.
They communicate over a BMI bus using registers to comunicate, the F registers sent by the CNC are read by the PMC and the G registers sent by the PMC are read by the CNC.
For example the cycle start button is an input into the PMC, this is conditioned by the PMC however the machine tool builder wants to, (not Fanuc) it is then sent over to the CNC via a G register using a designated bit.
The CNC side is pre-writen, but the PMC is writen by the machine tool builder or Retro-fitter.
If you can view the PMC ladder you should be able to find the F register bit as a contact in a rung or a word in a register.
Al.

[steve-o]

Cheers for that Al,

So, as these are instructions from PMC to CNC and vice versa, I won't be able to see what manipulates the signals (ie; an output contact)?

Would an axis movement for example correspond to an F code output change?

Cheers.
Steve.

[Dan Fritz]

The F outputs to the PMC are defined in the Fanuc Connecting Manual. There are bits for many different purposes, but they do not include things like the current X, Y, or Z axis position. The F registers include things like M, S, and T-codes (in BCD format), machine status bits, etc. Basically, any of the things that the CNC needs the PMC to execute on the machine.

For example, when the CNC executes an M-code in the program, it sends the BCD code for that M-code to the PMC using two bytes (16 bits) in BCD format, then turns on a "strobe" bit called "MF". The PMC is then supposed to decode those two bytes of BCD data to determine what the M-code is, then execute that M-function on the machine, then reply to the CNC with the "finish" signal (a G-register flag) called "FIN". When the CNC gets the FIN signal from the PMC, it knows that the PMC has finished executing the M-function and it will continue with the next block of the program.

When the PMC needs to send a real output signal to the outside world, or when it needs to read an input from the IO module, it uses the X or Y registers. The F and G registers are only memory bits that the CNC and the PMC can share, and they are not associated with any IO hardware.

[Al_The_Man]

Originally Posted by steve-o So, as these are instructions from PMC to CNC and vice versa, I won't be able to see what manipulates the signals (ie; an output contact)? .

Only inasmuch as viewing the rung that the F bit or register will affect, which ultimately would be a PMC Y output for example.
Al.

[steve-o]

Cheers chaps,

think you've managed to satisfy my curiosity!!!

Much appreciated.

Steve.