AC800M, PM860, MODBUS RTU

Hello, thanks for your reply to my original quesiton.

I have tried to setup a simple read block to see if i can establish a connection with no success. Unfortunatly my expirience with Controll builder and AC800M is fairly limited so any help i can get to complete this project is appreciated.

The slave device im using is the ABB CB PR123, the data sheet for the modbus memory map for the device is found in this pdf http://www05.abb.com/global/scot/scot209.nsf/veritydisplay/9154a4bc3e1da39ac125
78b100651462/$file/1sdh000556r0001.pdf

The PM860 modbus port is com3, the com3 port is using RS232 standard for sending, and the PR123 is using RS485, i am using a simple converter between the devices, this should cause any problems?

I have added some image files on how i have constructed my program and what variables i am using, if i have understood it correct in the read adress input should be qw247#700, if i want to read function 700 on slave device ID247, but i have no success.

First prio is to establish a connection to see if communication is even possible, and then start to read and write.

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PM860 Rank: 990

Asked 5 years ago

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You need to toggle MBRead_1.Req each time you want to read a block of data. You cannot connect it to "Enable_Com"

1. Connect "Error" of MBConnect_1 to a variable called "ERR"

2. Insert an AND after MBConnect_1

3. Insert a PulseGen after AND

4. Pulsegen Enable = STA and NOT ERR

5. Connect output of PulseGen to MBRead.Req

6. Set suitable period & pulse times for the pulse gen to read data at the required rate.

The Pulsegen will generate read requests whenever the connection is valid and there is no error on the MBConnect block.

To check error status codes on the MBConnect and MBRead blocks just search for the error code ( in your case "-5324" ) in the on line help. This trick works for any status code on any block.

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by PM860 Rank: 990 on 3/5/2015 1:23:51 AM | Like (0) | Report

Thanks for your answer, ive implemented what you suggested in my program and it the MBConnect, and pulsegenertor seems to be working as it should.

Still i have no success in communicating with my slave device, my start adress variable is "%qw247#30701", I want to read from slave device 247 and register 30701. The NDR output is false and (it should be true when data is ready if i understand it correctly) on the status i get code -30, the help topic states that error code 30 is when a invalid parameter is specified, or an invalid character has been used.

The RD(1) input on the MBread block is where the data form the slave device is returned? How do i expand this, I have seen that you can have several variables connected to the RD(1), RD(2)....RD(n) the block in my program only appears with a RD(1) input.

by Rob Lyon Rank: 2 on 3/5/2015 4:59:04 AM | Like (0) | Report

Slave is 247
Address is %qw#701
The leading 1,2,3,4 in modbus addressing is readundant and can usually be ignored.
Right click on the block and edit parameters ir change the block declaration to be mbread[5]

by PM860 Rank: 990 on 3/6/2015 3:27:46 AM | Like (0) | Report

Okay, now im ive configured the blocks as suggested and ive gotten the PLC to send read/write commands, but now i get the eroor code -4929 "Timeout. no answer from slave". I have checked baud rate, parity, stop bits and slave ID, it all seems to match the settings on my slave device. Could it be due to me writing the commands wrong or is it most likely the physical connection between the two devices. Since the PM860 uses rs232 standard via ethernet cable, i have to use a ethernet to rs232 9 pin and 9 pin rs232 to rs485 to be able to connect the PLC with the circuit breaker.

by Rob Lyon Rank: 2 on 3/6/2015 4:55:32 AM | Like (0) | Report

Use the programming cable. This is the correct pin out.

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