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sb234

FX3U 485 Modbus Slave

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I'm using the FX3U-485ADP-MB module set up as a slave, but am not seeing any activity out of it. The ironic part is I just used one a few days ago as a Modbus master (a bit more complicated) and that went relatively smoothly. My modbus master is a 2wire 485 device and I've accordingly jumpered my send and receive terminals (A's together and B's together) at the PLC and set the slave module to 110 ohm resistance. The module shows it is powered, but the RD and SD lights never illuminate. I've even put in the simplest example program from the manual with no success - it's shown below: LD M8411 MOV H1081 D8400 (9600 BAUD, 8 DATA BITS, NO PARITY, 1 STOP BIT) MOV H11 D8401 (SLAVE MODE) MOV H1 D8414 (SLAVE NODE ADDRESS) MOV H11 D8415 (EVENT AND ERROR COUNTER AND EVENT LOG ARE STORED - HEAD ADDRESS DEFINED BELOW) MOV K100 D8416 (COUNTER AND LOG DATA STORED STARTING AT D100) I'm not getting any data stored in the D100 area. If anyone has any advice on this - I would appreciate it! Thanks, Steve

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Are you using Channel 1 or 2? If a Comm Board already exists you should be using D8420 etc. Also these are just the comm setting whe're is your ADPRW command? Edited by Gambit

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I'm just using channel 1 - not doing any other comms. The ADPRW command is only used for Modbus master. The manual says you'll get error code 217 (illegal command) if using it with Modbus slave. I've tried both the default settings of register mapping (Mitsi to Modbus) and also custom settings using the D8470 + registers where you set your register type, quantity of blocks and then the head address (i.e., MOV H4 D8470 - 4 blocks/64 registers of M coils ; MOV K100 D8471 - head address of M100), but haven't had any success with either yet.

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Sorry, Didn't read it properly. I thought you we're master. I think you should check your cables, master and FX3U-485ADP-MB module. If a signal is send even without a programn then the RD LED should blink Edited by Gambit

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No problem - I appreciate the input! I did recheck my wiring - I actually wound up connecting to FX3Us through Modbus and things are working at least better. I'm having success reading (M) coils, but so far not holding (D) registers. I'm working with Mitsi on a resolution - which hopefully will be soon...

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