Constructing MODBUS ASCII Strings

Projects Networking, Protocols, and Devices
1

Hi all,

I am working on a project to communicate with a MODBUS ASCII device, but having trouble with accessing registers over 255. I understand if I want to access registers 1-5, the transmission is ":010300000004F8". I also understand that if I want to access registers 254-255, the transmission is ":010300FD0002FD". However, the device I need to access has registers at 1437, for example. How do I construct the transmission string for this?

Thanks!

2

The solution is that all 4 digits after the command function (03 above) are dedicated to the start register. For instance, if the start register is 11, these 4 digits will be 000A. If the start register is 1437, these 4 digits will be 059C. If the start register is 7895, these 4 digits will be 1ED7.