Rockford

Call ot Old Timers A0J2 & DOS MEDOC

6 posts in this topic

Any old timers out there that can dust off the memories and help me program an old A0J2 processor?

I can access the processor through Virtual Box DOS and MELSEC MEDOC.  I can upload the program and data registers and print everything.  The problem is that I want to change the program and having issues with the software & PLC.  The PLC has a ROM in it (ROM not an EPROM or EEPROM).  I can remove the ROM and set the jumper to RAM instead of ROM.  When I try to download the program I get "Param different" and the download stops.  I can reinstall the ROM and the PLC reloads OK and runs the program.  Where can I view/download/change the "Parameters" that the message is referring?  Do I need to clear the PLC somehow and reload everything?

Any help is greatly appreciated.  Thanks in advance.

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Is it possible that the ROM program is bigger than the PLC memory?

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Wow.  I haven't heard of that processor in MANY years!  One thing to think about:  Do you know what the plc was originally programmed with?  The dedicated programming units (GPP?) also known as the "big orange programmer", were widely used before the prices of PCs came down.  When I first got into this business, they were still quite popular - especially with the automotive plants.  The GPPs were able to access parameters that Medoc was not able to.  The biggest parameter set I had problems with were the MELSECNET/MINI parameters.  If a machine was programmed with a GPP and then someone used MEDOC to upload and download, the MELSECNET/MINI devices would no longer work.  The only way to get them to work was to add TO/FROM lines in the logic to set up the network.  The TO/FROM logic replaced the tabular settings available in the GPP.

All that said, if the machine was set up originally with a GPP, there could be a parameter that Medoc cannot access and therefore give you a mismatch.

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Thanks for the reply. 

This machine was made and programmed in Japan in the early '90's  I would assume that a GPP was used at that time. 

Do you know if there is a way to completely clear the memory, including all the parameters and start from scratch?

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You should be able to completely clear it by removing the ROM, unplugging the backup battery (if installed) and removing power from the unit for at least 30 minutes.  It has been a while since I regularly supported Mitsubishi products, but their RAM seemed to be backed up for a long time using a capacitor circuit that allowed change out of the battery without losing the RAM.  Even though you have a ROM module, the program is loaded into RAM upon power-up.

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14 hours ago, Rockford said:

Do you know if there is a way to completely clear the memory, including all the parameters and start from scratch?

The desire to program this fossil from scratch looks like strange, because according to the T99-0069 technical bulletin a production of this PLC series has been discontinued since September 2008 and the ME repair service for it is unavailable since September 2015, so to replace the CPU with Q-serie (totally or partially) would be a correct step. But... with your issue the A0J2H Hardware manual refers to ACPU Programming Manual (Fundamentals), where is written, that PLC Parameter data is stored in the head of user memory area. May be these User's and Programming manuals could be also helpful for your work (list of other manuals to this PLC serie is inside).

Edited by Inntele

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