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BITS N BYTES

PID CONTROL INSTRUCTIONS

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Does anyone have experience with these instructions. Trying to understand how the PID[190] instruction works! After reading the description in the CJ1 Instruction Set Manual W340-E3-04 I am still confused. Anyone have a clearer description or example of how it works and is formatted? My application is to control the Axis Speed in a Position Control Unit in stepper mode. I know the Current Position [D100] and the Target Position [D200] and need to modify the Speed [D300] with the PID instruction [starting at [400] to change the rate at which the Target position is reached. I believe the basic instruction to achieve this are:- MOV D200 D400 (Move the Target Position to first parameter word of the PID) PID D100 D400 D300 (Modify the Speed [D300] to close the loop between the Targeted Position [D200] and Current Position [D100]. I am really confused by description of the Input Ouput range in the sixth data word of the instruction. In my case this is bits 08 to 11 for Input and bits 04 to 07 of D406. Is this some kind of filter that ignores the higher bits of the Input and Output word? In other words if bits 08 thru 11 are OFF the upper 8 bits of the Input D400 are ignored. Therefore if D400=26000 (decimal)=6590Hex, only 0090Hex or 144 Decimal are used within the PID routine. How is the Work Area [in the above case D409 thru D438] of the PID instruction utilized? Is it automatically handles by the PID instruction itself or does it require external data? Any clearer explanation than available in the manual would be most welcome! BTW - you can probably tell from my recent posts I am a new Omron user [Only AB for the last 20 Yrs]. This is a great site with a wealth of useful information. Many thnxs to to all for their input.

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After exhaustive testing and rereading the manual I found the problem with PID(190) There is a mistake in the manual that screwed me up. Section3-18 page 682 shows the PID Parameter Table. This states that Bits 00 to 03 of C+6 are for the Integral and Derivative units and Bits 04 to 07 of C+6 are for the Output range. WRONG!!!! Bits 00 to 03 of C+6 are for the Output range and Bits 04 to 07 of C+6 for the Integral and Derivative units. The table on page 679 is correct. Checked the table on page 692 PIDAT(191), this shows the CORRECT format.

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I started to say that it was fixed in Revision 6 and to point you to the Omron Website. But when I went there I found it was Rev 4. Here's a link to Revision 11. W340-E1-11 CS-CJ Instruction Referension Version 3 CPUs @ MrPLC.com

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Sorry for late reply, you were correct in the manul errata... in the meantime have a look at this thread also... OMRON PID Instruction

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Jay I have downloaded all the manuals I need for my new application directly from the Omron website. Would have saved a LOT of grief if they kept them up to date. Where/when can one keep track of which is the latest revision? Looks like this website might be a more reliable place than Omron's to keep up to date! Thanks for your help.

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I have resisted duplicating manuals here which are available on the Omron website. (That last one was 22mb!) Their search engine is much better and it is suited for manual lookup. However, it's one of those circular priority needs. It's hot and then later, they need to be reminded. Basically, the Omron Document Library website is updated when the new Omron Tech CD revision is released.

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