Meldas M500 PLC to ClassicLadder Translation

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09 Aug 2023 20:19 - 09 Aug 2023 20:33 #277471 by tropostudio
Looking for some guidance on translating Mitsubishi Meldas M500 PLC into  ClassicLadder in LinuxCNC. Meldas designates X device types for input bit signals.  In the Howa VMC ladder docs for my VMC, it is apparent they used X both for hardware/physical inputs as well as for internal /software inputs.  Similarly, Meldas uses Y devices for output bit signals for both hardware and internal output signals. .Meldas  uses M devices for temporary bit memory (see attached image). My Howa VMC Axis test interface currently has all hardware inputs and outputs set up as HAL pins, and all work correctly. My assumptions for CL conversion:
  • Meldas X hardware/physical inputs become CL %Ixxx HAL inputs.
  • Meldas X software/internal inputs become CL %Bxxx bit memory.
  • Meldas Y hardware/physical outputs become CL %Qxxx HAL outputs.
  • Meldas Y software/outputs outputs become CL %Bxxx bit memory.
  • Meldas M bit memory becomes CL %Bxxx bit memory.
Does this sound correct?



It appears the  Meldas M500 PLC uses Data Register (D) devices for Word storage on arithmetic operations, and File Register (R) devices for storage of Word variables. These are both temporary. Sample rung below from the Howa VMC ladder docs shows a 16-bit transfer of a hex  value to a temporary File Register.
  • I assume this could be converted to a Variable Assignment operation in CL.  Is this correct?

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There are also Registers for storage of 'permanent' Word variables, some accessible as full 16 or 32 bit Words, and others accessible at the bit level within a Word. 
  • I assume any CL variables that need to be stored 'permanently' would need to be written to a HALfile.  Is that correct? 





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Last edit: 09 Aug 2023 20:33 by tropostudio. Reason: pics were too large and typos

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11 Aug 2023 16:44 #277646 by dm17ry
R file registers are not temporary storage - they are PLC<->NC interface. i there should be a map in some manual, i couldn't quickly find one..
but from the m60 manual e.g. R156 holds "overtravel ignore" bit map
so they will also map to HAL pins...

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11 Aug 2023 18:03 #277653 by tropostudio
Thanks - that makes sense. From the M500 PLC Programming manual, I gather file registers range from R0-R8191, and it is only R2900-R2947 that are user programmable at the bit level.

Not sure I can find a Mitsu doc with M500 register mapping. That shouldn't matter, as I have Howa VMC ladder printouts and their associated Register list with comments. It lists ~30 Register devices.

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