Communication of 85XX+ Temp. Scanner with VISION 120 PLC over Modbus RS485

[RAKESH GIRI]

Before we were using masibus 85xx  temp scanner with vision 120 PLC but now we are using masibus 85XX+ Temp. Scanner with VISION 120 PLC over Modbus RS485.But PLC not communicating with scanner. We don't find the address for scanner in PLC program.

[kratmel]

Please post order code for old and new temp scanner.

For find modbus address please use Visilogic Modbus sample project from Visilogic Help.

[RAKESH GIRI]

old scanner was 85xx

new one is 85XX+AIANNNU11XNN

[Ausman]

Quickly reading the scanner's manual there is reference to needing to use the available special program to set the scanner parameters.

https://www.masibus.com/data-acquisition/multi-channel-scanners/8-16-24-channel-scanner-protection-relay-cum-data-logger-85xx/

[RAKESH GIRI]

how can I change slave ID address in visilogic program.

masibus old scanner register is 400001 and masibus new scanner register is 300001.

how to put new scanner register value in vision 120 PLC  program.

 

bn.vlp

[Fernando Castro]

I think you are confusing the terms:

 

slave ID is usually used to specify the device on the Modbus Network. in the code that you sent is hardcoded to be 1:

 register 400001 and 300001 to me sounds like different function code registers. are you sure that the Masibus Old and New scanner uses different addresses?

some background on Modbus:

Modbus works using specified registry addresses, and the called function codes:

so, 30001 is the first address on the Input registers, and 40001 is the first one on the Holding registers.

the difference is that holding registers are Read/Write  and Input registers are only Read.

so, if you want to access register 30001 you need to point to addres 0 of Input registers using function code 4 (Read Input registers).

the program that you sent is accessing address 0 using function code 3 (Read Holding registers) which happens to be register 40001:

 

If you are sure that you need to read register 30001 then use the appropriate function code:

 

Also, some Modbus devices starts counting on 0, others on 1 just to take into consideration.

[RAKESH GIRI]

thank you so much sir for resolved my problem.

[RAKESH GIRI]

On 3/31/2023 at 6:05 PM, Fernando Castro said:

I think you are confusing the terms:

 

slave ID is usually used to specify the device on the Modbus Network. in the code that you sent is hardcoded to be 1:

 register 400001 and 300001 to me sounds like different function code registers. are you sure that the Masibus Old and New scanner uses different addresses?

some background on Modbus:

Modbus works using specified registry addresses, and the called function codes:

so, 30001 is the first address on the Input registers, and 40001 is the first one on the Holding registers.

the difference is that holding registers are Read/Write  and Input registers are only Read.

so, if you want to access register 30001 you need to point to addres 0 of Input registers using function code 4 (Read Input registers).

the program that you sent is accessing address 0 using function code 3 (Read Holding registers) which happens to be register 40001:

 

If you are sure that you need to read register 30001 then use the appropriate function code:

 

Also, some Modbus devices starts counting on 0, others on 1 just to take into consideration.

Dear sir, we put the read input register (4) but also not communicated with scanner. Please find the attached photo and program. 

bn.vlp

[RAKESH GIRI]

how can I change slave ID address in visilogic program.

masibus old scanner register value is 400001 and masibus new scanner register value is 300001.

we put new scanner register value in vision 120 PLC program but PLC not communicated with scanner.

Please find the attached program, and please suggest me.

bn.vlp

[Gabriel Franco]

1. Do not place more than one rung in each net. Split them.  

2. You´re using the same ID (#1) to master and to slave. Fernando already mentioned where to change slave ID address.

 

It´s highly suggested to use Modbus PC software (such as ModScan, Modbus Poll or any other) to debug communications.

 

[Fernando Castro]

On 4/1/2023 at 3:07 AM, RAKESH GIRI said:

thank you so much sir for resolved my problem.

So, I did not solved the problem? 😂.

 

2 hours ago, Gabriel Franco said:

1. Do not place more than one rung in each net. Split them.  

2. You´re using the same ID (#1) to master and to slave. Fernando already mentioned where to change slave ID address.

 

It´s highly suggested to use Modbus PC software (such as ModScan, Modbus Poll or any other) to debug communications.

 

Good catch! from @Gabriel Franco. I assumed that the program was working as it was with another older scanner before.

If that is the case, the process that I'll do to troubleshoot is first. check the hardware configuration.

I have the feeling that the issue may not be the Modbus address that you are trying to read (30001 vs 40001).

If it is RS485, then it is a serial communication is the scanner properly configured? (Baud rate, parity, data bits, timeout) does it require a terminator resistor? sometimes there is a configuration option or dip switch to set those.

And following Gabriel, you can test on a computer using this Modbus Master simulator: Modbus Master Simulator - free software utility for testing Modbus slave devices (dxp.pl)