Hi all
I have to carry out a program mod to a Melsec A2N CPU but having only Siemens experience i am unsure about the arrangement of program memory of Mitsubishi CPUs.
Unlike Siemens where ROM takes presidence, the Melsec CPU seems to be switchable between ROM and RAM via a DIP switch.
The memory module has 2 removable ICs which i assume are EPROMs because they have small stickers over the center windows. These are labelled up ODD and EVEN - i think this referes to parity but i dont know why - does any one know?
I assume that when switched to ROM mode, the program on the EPROM is scanned by the CPU and if i were to upload the program to GX Developer, i could modify it, switch CPU to RAM mode and download the modified program. As long as the battery is ok i assume that after every cold restart the CPU would then scan the modified program in the RAM.
Most importantly, if it all went pear shaped i assume i could just switch back to ROM mode and the original program would be scanned from the EPROM. Presumably the program on the EPROM cannot be altered and will always be a reliable back up.
I would be most grateful if someone with A Series experience could let me know if i am correct in all my assumptions.
Best regards
Jim
I have to carry out a program mod to a Melsec A2N CPU but having only Siemens experience i am unsure about the arrangement of program memory of Mitsubishi CPUs.
Unlike Siemens where ROM takes presidence, the Melsec CPU seems to be switchable between ROM and RAM via a DIP switch.
The memory module has 2 removable ICs which i assume are EPROMs because they have small stickers over the center windows. These are labelled up ODD and EVEN - i think this referes to parity but i dont know why - does any one know?
I assume that when switched to ROM mode, the program on the EPROM is scanned by the CPU and if i were to upload the program to GX Developer, i could modify it, switch CPU to RAM mode and download the modified program. As long as the battery is ok i assume that after every cold restart the CPU would then scan the modified program in the RAM.
Most importantly, if it all went pear shaped i assume i could just switch back to ROM mode and the original program would be scanned from the EPROM. Presumably the program on the EPROM cannot be altered and will always be a reliable back up.
I would be most grateful if someone with A Series experience could let me know if i am correct in all my assumptions.
Best regards
Jim
