Hello!

Could someone mention which are the main advantages of a 32bits format for modbus map instead of 16 bits format?32 bits format is standard modbus (developed by MODICON) or it's a Daniel modbus or something else?

Thank you!

 

32 bits gives you larger numbers. You can store a 32 bit number in a standard Modbus map by just splitting the number between 2 16 bit registers. That is, you could for example put 2 of the 4 bytes in holding register 5000, and the other 2 bytes in holding register 5001.

There are some non-standard implementations that have some 32 bit registers, but they seem to be rather rare outside of certain specialized markets.

When the Modbus message goes down the wires, it's just a stream of bytes. The question becomes whether the software in the devices at your end points can assemble 32 bit numbers from adjacent registers and make use of them.

Most analogue field devices don't have more than 10 or 12 bits of resolution and for those that do, getting 16 bits of meaningful accuracy out of real world devices is a real challenge. This means that the problem seldom comes up in practice.

The main application for larger numbers seems to be for counting very large quantities. In those cases, the data handling methods seem to be very device specific.