Modbus TCP Master via USB
Click here to see this page in full context

Variable address range

IEC variable address range

The following table lists the equipment variable address range if you have selected the IEC61131 Syntax.

 

Device

Bit Address

Word address

32

bits

Remarks

%KW

%KW00000:X00 - %KW65535:X15

%KW00000 - %KW65535

or

*1 

*2

%MD

------

%MD00000 - %MD65534

 

%MF

------

%MF00000 - %MF65534

 

%M

%M00000 - %M65535

------

 

%MW

%MW00000:X00 - %MW65535:X15

%MW00000 - %MW65535

 

%S

%S000 - %S000

------

*5 *6

%SW

%SW000:X00 - %SW999:X15

%SW000 - %SW999

 

*1You can set the data storing order in 32-bit data word units and 64-bit data double-word units in the Device Setting dialog box.

*2Write disable

*5Read/Write, depending on the bit/word number.

*6To fit with equipment variable coding, the most significant byte could be chosen by the software.

 

NOTE

 

Non IEC variable address range

The following table lists the equipment variable address range if you haven't selected the IEC 61131 Syntax.

 

Device

Bit Address

Word address

32

bits

Remarks

Coils (C)

00001 - 65536

------

   

or

*1 

 

Discrete Inputs

10001 - 165536

------

*2 *3

Single word Input Registers

30001,00 - 365536,15

30001 - 365536

*2

Single word Holding Registers

40001,00 - 465536,15

40001 - 465536

*3 

Double word Input Registers

30001,00 - 365536,15

30001 - 365536

*2

Double word Holding Registers

40001,00 - 465536,15

40001 - 465536

 

*1You can set the data storing order in 32-bit data word units and 64-bit data double-word units in the Device Setting dialog box.

*2Write disable

*3When you write to the bit address, the Display reads the entire word, sets the defined bit, then returns the new word value to the External Device. If the ladder program writes data to this word address during the bit write process, the resulting data may be incorrect.

 

IEC equivalents

The following table gives the equivalents between the Modbus syntax and the IEC61131 syntax.

 

Device

MODBUS Syntax

IEC61131 Syntax

Format

Range

First element

Format

Range

First element

Internal coils and Output coils

00001+i

i = 0 to 65535

00001*1

%Mi

i = 0 to 65535

%M0

Holding register (word)

40001+i

i = 0 to 65535

40001

%MWi

i = 0 to 65535

%MW0

Holding register (word bit)

40001+i,j*2

i = 0 to 65535

j = 0 to 15

40001,0

%MWi:Xj

i = 0 to 65535

j = 0 to 15

%MW0:X0

Holding register (double word)

40001+i

i = 0 to 65534

40001

%MDi

i = 0 to 65534

%MD0

Holding Register (float)

40001+i

i = 0 to 65534

40001

%MFi

i = 0 to 65534

%MF0

Holding register (string)

40001+i

i = 0 to k*3

40001

%MWi

i = 0 to k*3

%MW0

*1Leading zeros "00001" must be preserved.

*2j is a bit index with the following convention: 0 for the least significant bit and 15 for the most significant bit.

*3k is equal to 65535 - string length / 2 rounded to the upper value For instance with a 11 characters string we've got 65535 - 6 = 65529.

 

NOTE

IEC61131 Syntax Address Mapping

Address mapping in BLUE is as follows. %MD and %MF use two sequential words form the specified address. The %KW, %KD, and %KF are mapped similarly.

 

Supported Function Codes

The supported function code list is shown below.

Function Code (Hex)

Description

FC01(0x01)

Read the ON/OFF status of the slave coil (0X).

FC02(0x02)

Read the ON/OFF status of the slave discrete input (1X).

FC03(0x03)

Read the description of the slave holding register (4X).

FC04(0x04)

Read the description of the slave input register (3X).

FC05(0x05)

Change (Write) the slave coil (0X) status to either ON or OFF.

FC06(0x06)

Change (write) the description of the slave holding register (4X).

FC15(0x0F)

Change (Write) the slave consecutive multiple coils (0X) status to either ON or OFF.

FC16(0x10)

Change (write) the descriptions of the slave consecutive multiple holding registers (4X).

NOTE