A2U cpu rom question?

[Guest -guest-]

Hi, I was wondering if anybody here can explain how the ROM works on a mitsi A2U cpu? Basically I am fault finding on a machine fault, the plc program is stored/running in the TWO rom chips, odd and even. When I try to look at the program ladder using medoc (all I have!) am I downloading the WHOLE program from ram? If I wish to make changes, can i transfer the program to medoc, make changes and transfer back to plc, remove eproms and switch over to run from ram? is this possible or am I missing something important? Any help greatly appreciated. A humble sparky.

[panic mode 246]

Thant's not all, you have to change settings so CPU know where to look for the program. Take a look at the User's Manual IB-66436. Section 5 deals with RAM/ROM memory, settings etc.

[navillusi 2]

Question: What type of chips are fitted to the PLC? You can have EEPROM or RAM fitted and I have personnaly mistaken an EEPROM for a RAM (oops) on the An series. Is the PLC battery backed? If so it could be a higher chance that you have RAM If the are EEPROM's you must write the program to the EEPROMS using MEDOC and the same applies if they are RAM chips. You cannot remove the EEPROMS and not replace them with anything, you must replace them with RAM chips. The program has to be stored somewhere. In answer to your other question, yes, the whole program is transferred (from whatever memory) when uploading with MEDOC