Chapter 6 Modbus RTU protocol
60
Inquiry (master side)
Slav
e
addr
ess
Func
tion
Initial
address
Memory
quantity
Num
ber
of
byte
Data
Data
Error check
(CRC16)
High
Low
High
Low
High
Low
High
Low
Low
High
11 H 10 H 00 H 00 H 00 H 02 H 04 H 00 H 0A H 00 H 0A H
** H
** H
Answer (slave side)
Slave
address
Functio
n
Initial address
Memory quantity
Error check
(CRC16)
High
Low
High
Low
Low
High
11 H
10 H
00 H
00 H
00 H
02 H
** H
** H
When you use a slave device to connect to an external device such as a PLC or touch
screen, use a single memory write function instead of using multiple memory write
functions. However, in the PC loader, the minimum/maximum or base value of the
parameter is preset by inputting the specification.
6.7 Exception response - error code
If an exception occurs, after the setting (1) accepts the highest level of the command
(function), a response command is sent and each exception code is transmitted.
Slave
addre
ss
Functi
on
+80H
Error code
Error check
(CRC16)
Low
High
1Byte
1Byte
1Byte
1Byte
1Byte
CRC16
◆
Illegal operation function (error code: 01 H): Unsupported command
◆
Illegal data address (error code: 02 H): The starting address of the query data is
inconsistent with the address sent from the device.
◆
Illegal data value (error code: 03 H): The number of query data is inconsistent with the
