Mitsubishi F2-20GF1 Question

Hi Guys
I have an old F2-20GF1 (V2) interface unit.
I have not used it for quite a few years But I only ever used it on F1 PLCS.
I understand there were some ROM units that were usable with this Interface.
What were the ROMs for and were did they fit , i never seen them or had to use one.
Can any remember that far back???
Cheers
ian

The ROMs were used with the original F Series PLCs before the F1 and F2 models were introduced. There was a ROM chip for each PLC model and these had to be plugged into the PLC before the 20GF1.

Thanks for that Andy.
Ian