YOKOGAWA VZ20X, User Manual

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IM 77V01B01-01EN 5th Edition: 2023.03.07-00
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PDU configuration
The PDU (Protocol Data Unit) comprises the following n bytes.
Byte No. 0 1 to (n-1)
Description Function code Data
Function code: Specify the command from the host device.
Data: Specify the register No. and number of internal registers, parameter values, etc.
according to the function code.
The following example explains action for function code 03.
(Example) Function code 03 Read multiple registers
For details on the response format when an error occurs, refer to the response error
code.
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Request (during normal operation) Read n items of data
MBAP Header PDU
Number of
bytes
2 2 2 1 1 2 2
Command
elements
Transfer
ID
Protocol
ID
Number of
bytes
Unit ID Function
code
Register
start No.
(Hex
number)
Number of
registers
(Hex) Arbitrary 0000 0006 01 03 n
The register start no. is the value obtained by subtracting 40001 from the register
number (reference number).
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Response (during normal operation)
MBAP Header
Number of
bytes
2 2 2 1
Command
elements
Transfer
ID
Protocol
ID
Number of
bytes
Unit ID
(Hex) Arbitrary 0000 2n+3 01
Continuation of response
PDU
1 1 2 2
Function
code
Byte
count
Register
content
... Register
content n
03 2n