Chapter 6 Communication Mode
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EH-SIO support function codes
The function code that EH-SIO supports shown in the following table.
Table 6.10 EH-SIO support functions
Function Code
Function
Broadcasting
01 (0x01)
Read Coil Status
State of coil is read.
-
02 (0x02)
Read Input Status
State of input status is read.
-
03 (0x03)
Read Holding Registers
State of holding register is read.
-
04 (0x04)
Read Input Registers
State of input register is read.
-
05 (0x05)
Force Single Coil
State of coil changes between ON/OFF.
OK
06 (0x06)
Preset Single Register
State of holding register is changed.
OK
15 (0x0F)
Force Multiple Coils
State of two or more coils changes between ON/OFF.
OK
16 (0x10)
Preset Multiple Registers
State of two or more holding registers is changed
OK
Exception code
When the contents of a query message are inaccurate or a slave cannot process the query, the slave returns an
exception response including error factor.
Table 6.11 Exception code list
Exception code
Item
Meaning
01
Illegal function
Requested function is not supported
02
Illegal data address
Specified data address does not exist in the slave.
03
Illegal data value
Data value is not allowed for the slave.
04
Slave device failure
An unrecoverable error occurred in the slave.
05
Acknowledge
Although query is recognized, it takes time to reply. (To prevent timeout
error.)
06
Slave device busy
Processing of previous query.
Reference : Modbus data address
Data address must be specified for data reading and writing. According to the “Modbus Protocol Reference Guide”
there are four types of data (coil, input status, input register, and holding register).
(1) Coil Bit data from 1 to 9,999 for reading and writing.
(2) Input status
Bit data from 10,001 to 19,999 for reading only.
(3) Input register
Word data from 30,001 to 39,999 for reading only.
(4) Holding register Word data from 40,001 to 49,999 for reading and writing.
Since data type is specified by function code, the address in message is only 4 digits. Moreover, if the address of a
message format is set to "0000", then the specified address is "x0001" (x being the maximum higher rank for each
data classification).
Ex.) Input register Data address 10789
4 low figures 789
Offset from Address 788
Specification of data address 0x0314
Hereafter, the explanation of each function code is written in accordance with this.
Содержание EH-150 Series
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