Chapter 8. Communication Function
8-78
Ex1) 00 0A 01 02
Function block input Input value
REQ Enter the input condition to operate
CH 16#1 or 1 Set channel (0, 1)
SLV_ADDR 16#11 or 17 Slave station
FUNC
16#10 or 16
Enter ‘16’ as bits are continually written on the Holding Register.
ADDR 16#01 or 1
Set the starting address to write on the slave station
- Write on no. 1 to write on, starting from the Holding Register
40002 in accordance with the previous no. 8) “Modbus
addressing rules.” And the highest data of the data address
doesn’t need to be input. Because it’s automatically processed
by the input value of the input FUNC of the function block.
NUM 16#02 or 2
Set the number of data to write on the slave station..
- As the example writes 2, of which hex is 16#0002. Input
16#02 for NUM.
z Result
Holding Registers
40003 40002
Registers status 16#0102 16#000A
5) Error codes
CODE Error type Meaning
01 Illegal Function Error in inputting function code in function block.
02 Illegal Address Error of exceeding the area limit of reading/writing on the slave station.
03 Illegal Data Value
Error when the data value to be read from or write on the slave station isn’t
allowed.
04 Slave Device Failure Error status of the slave station.
05 Acknowledge
It’s a responding code of the slave station for the master station to prevent the
master stations time-out error, when request command processing takes
time. The master station marks an error code and waits for a certain time
without making any second request.
06 Slave Device Busy
Error when request command processing takes too much time. The master
should request again.
07 Time Out
Error when exceeds the time limit of the communication parameter as it
communicates.
08 Number Error
Errors when data is 0 or more than 256 bytes, when the data size is bigger
than the array size, or when Number and BYTE_CNT are different from each
other.
09 Parameter Error Error of setting parameters (mode, master/ slave)
10 Station Error
Error when the station number of itself and the station number set by the
input parameter of the function block is the same.
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