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**Mach4 General Discussion / Re: MACH4 - Modbus **

« **on:**May 07, 2014, 01:00:22 AM »

The M4 modbus uses the newer Modicon table/register convention. Not the hex addressing that Mach3 used. There tables in the modbus spec that pertain to functions that operate on them. Modbus devices usually give the addresses in either hex addresses or the table/register format. And sometimes they will give both. Also, sometimes they prefix the addresses a bit differently.

Some do the T:RRRRR format where T is the modbus table and RRRRR is the base 1 register.

Others do a TRRRR format where an address may look like 40001. This is really table 4, register 1.

IMPORTANT: Addresses are base 0 and registers are base 1. The M4 modbus uses registers.

If the device documentation gives the old hex addressing format, convert the hex number to decimal and then add 1 (base 1 remember!). If the address is given in decimal, simply add 1.

Attached is a document that you may find useful.

Also, here is a good page that explains a lot. http://www.csimn.com/CSI_pages/Modbus101.html

Steve

Some do the T:RRRRR format where T is the modbus table and RRRRR is the base 1 register.

Others do a TRRRR format where an address may look like 40001. This is really table 4, register 1.

IMPORTANT: Addresses are base 0 and registers are base 1. The M4 modbus uses registers.

If the device documentation gives the old hex addressing format, convert the hex number to decimal and then add 1 (base 1 remember!). If the address is given in decimal, simply add 1.

Attached is a document that you may find useful.

Also, here is a good page that explains a lot. http://www.csimn.com/CSI_pages/Modbus101.html

Steve