# How to find address for ML 1200 for modbus or RS485

**URL:** https://discourse.nodered.org/t/how-to-find-address-for-ml-1200-for-modbus-or-rs485/71284
**Category:** Industrial
**Tags:** modbus
**Created:** [26 November 2022 14:06 UTC](https://discourse.nodered.org/t/how-to-find-address-for-ml-1200-for-modbus-or-rs485/71284 "2022-11-26T14:06:40Z")
**Posts on this page:** 1
**Showing post:** 23

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### Author: ![Steve-Mcl](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/steve-mcl/32/4826_2.png) [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)
#### Post date: [10 December 2022 12:24 UTC](https://discourse.nodered.org/t/how-to-find-address-for-ml-1200-for-modbus-or-rs485/71284/23 "2022-12-10T12:24:55Z")

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@akshayjain we are not here to do you job for you.

As colin rightly states this is for node-red help.

Clearly this is a work related thing and you should either be competent with PLCs or you should hire someone who is.

In the interest of getting past this, I will do your job for you.

It took me less than 2 minutes to find this info and about 10 minutes to write it up for you.

  

* * *

A quick search on google for "allen bradley ml1200 modbus mapping" resulted in finding [this](https://literature.rockwellautomation.com/idc/groups/literature/documents/um/1762-um001_-en-p.pdf) manual

Page 140 states...

> For more information on configurating your MicroLogix 1200 controller for  
> Modbus protocol, refer to the MicroLogix 1200 and 1500 Programmable  
> Controllers Instruction Set Reference Manual, publication 1762-RM001

Then I did a quick search on google for "1762-RM001"  
The VERY FIRST RESULT was a link to the manual: [https://literature.rockwellautomation.com/idc/groups/literature/documents/rm/1762-rm001\_-en-p.pdf](https://literature.rockwellautomation.com/idc/groups/literature/documents/rm/1762-rm001_-en-p.pdf)

Page 449 reveals how the AB PLC addresses are mapped to ModBus addresses...

 ![image](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/3/c/3cab581e5553800dd0394bc2858e702a2dbcf5b4.png)

Essentially, by default, it appears that

- N12:0 will be accessible by reading Address 1 `(*1)` using FC4 (Read Input Registers)  
N13:0 will be accessible by reading Address 1 `(*1)` using FC3 (Read Holding Registers)
- N10:0 will be accessible by reading Address 1 `(*1)` using FC1 (Read Coil Status)  
N11:0 will be accessible by reading Address 1 `(*1)` using FC2 (Read Contact Status)

But that might NOT be the case - you will need to check the actual PLC settings - never assume.

  

NOTES...

`(*1)` Sometimes the PLC maps address 0 to modbus 0, sometimes it is modbus address 0 is PLC address 1, sometimes it is modbus address 1 is PLC address 0, it depending on how AB have mapped things

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