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PV The double word "PV" contains the parameter value.
In the case of a read request, the value in the transmit data has no
significance. The receive data contains the parameter value.
In the case of a write request, the transmit data contains the value to
be written to the parameter. The receive data contains the parameter
value.
If a read request or a write request were not successful, the double
word "PV" contains the error number of the error.
Example: Reading a parameter In the example, the program number of the product is read from the
parameter _prgNoDEV. The parameter _prgNoDEV has the parame-
ter address 258 (01
h
02
h
).
The parameter value read has the decimal value 91200 which corre-
sponds to 01
h
64
h
40
h
.
Transmit data:
Ctrl Subindex Index PV
12
h
00
h
01
h
02
h
00
h
00
h
00
h
00
h
Receive data:
Ctrl Subindex Index PV
22
h
00
h
01
h
02
h
00
h
01
h
64
h
40
h
Example: Writing of an invalid
parameter
In this example, the value of a non-existent parameter is to be
changed. The parameter has the parameter address 101 (00
h
65
h
).
The value of the parameters is to be changed to 222 (DE
h
).
Before the slave can accept a new request, the value 02
h
must first be
transmitted in byte "Ctrl".
Since the slave cannot address the parameter, a synchronous error
message is transmitted with the receive data. Byte "Ctrl" is set to 72
h
.
Double word "PV" is set to the error number (error number 1101
h
:
Parameter does not exist).
Transmit data:
Ctrl Subindex Index PV
32
h
00
h
00
h
65
h
00
h
00
h
00
h
DE
h
Receive data:
Ctrl Subindex Index PV
72
h
00
h
00
h
65
h
00
h
00
h
11
h
01
h
See the product manual for information on the error numbers.
LXM32M
3 Basics
Modbus-TCP module 27
0198441113843, V1.01, 01.2012