whyme

The PC end may need 7 and 8 linking (RTS/CTS in loopback) depending on the software being run.

It shows that the Mitsubishi is bomb proof I admit but as a principle, hashing these two protocols together like this is not a guaranteed practice.  The voltage levels are too diverse.  Not all designers will have such a thorough protection circuit on their hardware.  To evade needing to have an RS232 to RS422 converter I do not believe that this is a valid technique.

If you have been at it long enough you find that you naturally develop a spreadsheet like the one you are talking about.  From a contracting point of view there is no point in re-inventing the wheel.  A customer would not appreciate you taking the time to do that.  Having said that, the documentation that you get from the equipment supplier should outline all of the groupings for you.  Admittedly the documentation is rarely to hand when you need it so in that respect a common format would be beneficial in the long term even if it cost more for the first job in the short term.  

If it has been written correctly, the chances are that a sensor is out, or reading out of limit, causing the code to halt.   It has probably been programmed to do what it is doing.  You just need to work through the code to find the issue.  

I communicate directly into the programming port using RS422 as I have the protocol from waaaaay back when (being old has it's advantages).  This way of accessing the device limits you to only be able to read and write the D Registers from D0 to D999 but with a bit of code in the plc you can jump around that and reach all of the registers.  The other point is that you can only run at 9600 e 7 1 serial speed and protocol.  But you can do a lot at that speed if you need to. The link technique is rock solid.  It has never let me down yet.  You can LAN enable the PLC if you use a Lan to RS232 converter (TIBBO do a good one) and link to the PLC through the HMI if you have one handy. The old E-Series are better at handling the through link compared to the newer units but the link takes priority over the HMI so no worries there.  If there is enough interest and can dig out the .pdf I have and post it if needs be.  Advice on the legality of sharing this type of data would be appreciated.  

I still prefer coding it from scratch.  It gives you more of a feel as to what the variables do in the process.  

The SC09 is an active unit converting the RS232 single ended protocol (which should be +/- 10 to 15Volt from the PC) to a differential output to the PLC (which runs between 0 and 5 Volts).  Using the simple cable identified at the start of this thread you will be relying on the PLC's input protection to limit the high RS232 voltages to the lower +/- 5 Volts.  This would not be how the PLC would have been designed to be used.    There are so many SC09 clones on Ebay and Amazon that do the conversion safely why take the risk of damaging the PLC? Captain buzz kill signing off.

When you say PID in gates do you mean code it from scratch using ladder?

Sorted.  An M register that I was assuming was triggering was being overwritten in the PC section of the ladder code so it was working but out of sequence.  Clearing the register so that it fired correctly got the code working again. It was just one of those things.  Talking about it it gave me the break I needed to figure it out.   Weird how the brain works sometimes. 

I have an FX3u16MR attached to two FX3u4AD units (right mounted).  I am running the first two channels of the eight in 12 bit mode, the next two channels in 16 bit mode, the next two channels in 12 bit mode again and the last two channels are idling.  All inputs are configured as 4-20mA.  Working with the first channel only for now, what I am finding is that I have to load the gains twice for them to take.  It points to a timing issue in the code that I am running in the plc.   It just seems to have started happening though.  Admittedly I am recoding so the ADC calibrates from a HMI rather than from a PC trigger which is what I had before.  But I have just paralleled up the M register that invokes it.  I am working through the code as I speak. If anyone has any idea's i would love to hear from you.  I know this bit of kit fairly well I am just missing something here and it is bugging me.  A problem shared and all that. Thanks in advance.  

There are units that you can bolt on to the programming port of an FX PLC that will set up a VPN automatically.  A similar unit at the control end (your offices) would be able to poll the rest of the units in the field and grab any alarm information that you need. You could even run it from a spreadsheet. PM me if the project is still in flux and you need more details.