M8411 FLAG

[russ3654 0]

I installed the FX3U-485ADP-MB module, checked my revisions since I read posts from the past about this bit not turning on. I have GX developer 8.78G rev, the PLC has rev 2.4. I wrote the program per example from the Modbus manual (JY997D26201A) page 28. Went into PLC system 2 parameters and made the settings. I wrote a program line for M8411 to set a bit and turn on output Y0, it never happens, any ideas would be greatly appreciated. I'm showing no comm errors in M8402/M8403/M8063.

[Crossbow 297]

Do you have a BD board installed? You cannot use left side bus modules without the BD board. And which channel number are you trying to use Modbus on?

[russ3654 0]

I have the FX3U-CNV-BD plugged into the PLC and the FX3U-485ADP-MB module plugged into that, I'm set up to use channel 1. Should the M8411 bit set upon intial scan or power-up of the PLC? In my PLC PARAMETER; PLC system 2 I can't find supporting documentation on the settings could my probblem be there? Does anyone have a general test program I can load to see if the bit sets, to see if I'm dealing with a hardware or software issue? What is the micro looking for to set the M8411, when it sees the ADP module does this set it, because all the program code to configure comm settings to send messages to the slave needs this bit set. I'm using the program from the Mitsu Modbus manual for master set up. In the manual it stated "LD M8411" do I need to write a line of code to initiate the loading if so how should it read? My send LED flashes on the ADP module and my network LED flashes on the slave. I also have a E-Net module comunicating with the HMI (Mitsu Tech support said this won't cause a problem with modbus) Edited 22 Sep 2010 by russ3654

[Crossbow 297]

This is directly from the Modbus manual JY997D26201-A. Section 5.4 on communication setup. 3. Using the MODBUS Configuration Request Flag (M8411) The Auxiliary Relay M8411 is a special relay used for MODBUS Serial Communication setup only. Do not use the PLC ladder program or any other External Devices to set or reset this relay at any time. Do not use any coils or conditionals before the MODBUS Configuration Request Flag or between the MODBUS Configuration Request Flag (M8411) and the MOV commands. Using other coils or conditionals before or after the MODBUS Configuration Request Flag during Communication Setup will invalidate the MODBUS Communication Parameters and thereby disable MODBUS Serial Communication. So it appears the PLC will turn this flag on automatically when the port gets configured for Modbus function, and you will use it to run the configuration routine as shown in the manual. The code in section 5.2 of that manual seems pretty clear to me. Section 11.1 shows a working example of many of the Modbus functions.

[russ3654 0]

I've read and applied that, but if the flag M8411 does not turn on D8400/D8401 etc will not recieve the config info, so how can the "port get configured for Modbus Function" when no information was sent to D8400....etc, because the M8411 flag must turn on to execute the MOV commands, My program is exactly the same as the example, but the M8411 flag never turn on, the MOV commands are never executed. Is it not seeing the ADP module, I'm programming threw my E-net module is that causing a glitch. Edited 22 Sep 2010 by russ3654

[russ3654 0]

Installed a different ADP Module, it works settings MOV into Data registers