Modbus is a serial communications protocol originally published by Modicon (now Schneider Electric) in 1979 for use with its programmable logic controllers (PLCs). Simple and robust, it has since become a de facto standard communication protocol, and it is now a commonly available means of connecting industrial electronic devices.(From Wekipedia)

## Address Mapping

Modbus has four types of address: Coil, Discrete Input, Input Register and Holding Register.

Modbus has two address description method: standard and extend.

The following table could show the full address discription in Modbus.

Type	Standard	Extend
Coil	00001-09999	000001-065536
Discrete Input	10001-19999	100001-165536
Input Register	30001-39999	300001-365536
Holding Register	40001-49999	400001-465536

Standard and Extend address description are all supported in Modbus.Net.Modbus. The only difference is don't write too large number in address.

The following table shows how to write address in Modbus.Net.Modbus

Standard Modbus Address	Modbus.Net.Modbus String Address
00001	0X 1
00002	0X 2
09999	0X 9999
065536	0X 65536
10001	1X 1
30001	3X 1
40001	4X 1

## Address Coding

In Modbus.Net, you can write "0X"(Coil), "1X"(Discrete Input), "3X"(Input Register), "4X"(Holding Register) in Area.

Don't forget to type a space between Area and Address.

If you want to use subpos, type string address like this:

4X 1.12 (Area Address.Subpos)

## SubAddress Rules

For 0X and 1X, the scalation is 1/8. This means each address is bool.

Noticing that you can only read 1X.

SubAddress System is not activated in 0X and 1X.

For 3X and 4X, the scalation is 2. This meas each address is short.

The number of SubAddress is from 0 to 15.

Caution: Modbus.Net.Modbus SubAddress has a giant difference towards standard Modbus.

Bit position from Modbus.Net is one less than standard modbus.

Standard Modbus

1 0 1 1 1 0 0 0 1 0 0 0 0 1 1 0 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

Modbus.Net.Modbus

1 0 1 1 1 0 0 0 1 0 0 0 0 1 1 0 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0