Sinee EM730 Series, Руководство пользователя

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User Manual of EM730/EM730E Series Inverter
324
1.1.1.4 0x08: function code for diagnosis
The Modbus function code 08 involves a series of tests to check the communication system
between the client (master station) and server (slave station), or internal error statuses of the
server.
The test to be executed is defined by the sub-function code fields of two bytes in the
request. The server makes responses properly.
Copy the function codes and sub-function codes. Some diagnoses will enable the remote
terminal unit to return the corresponding data through the data field in normal response.
Under normal circumstances, when the diagnosis function is sent to the remote terminal
unit, the user program in this remote terminal unit will not be affected. The user logic cannot be
accessed by diagnosis, such as: discrete magnitude and register. The error counter in the remote
terminal unit can be remotely reset by applying some functions.
The main diagnosis function used by our company is line diagnosis (0000), which is
used to test the normal communication between the host and slave.
The normal response to
a request to return query data is to return the same data. At the same time, the function codes and
sub-function codes are also copied.

Request PDU
Function code 1 byte
0x08
Sub-function code 2 bytes 0x0000 - 0xFFFF
Data 2 bytes 0x0000 - 0xFFFF

Response PDU
Function code 1 byte 0x08
Sub-function code 2 bytes 0x0000 - 0xFFFF
Data 2 bytes 0x0000 - 0xFFFF

Error PDU
Error code 1 byte
0x88
Exception code 1 byte See Table 4-33

Sub-function code