RKC INSTRUMENT Z-TIO-G, Инструкция по эксплуатации

Страница: 68 / 246

7. MODBUS
IMS01T28-E4
7-4
7.1.4 Slave responses
(1) Normal response

In the response message of the Read Holding Registers, the slave returns the read out data and the
number of data items with the same slave address and function code as the query message.

In the response message of the Preset Single Register, the slave returns the same message as the query
message.

In the response message of the Diagnostics (Loopback test), the slave returns the same message as the
query message.

In the response message of the Preset Multiple Registers, the slave returns the slave address, the function
code, starting number, and number of holding registers in the multi-query message.
(2) Defective message response

If the query message from the master is defective, except for
transmission error, the slave returns the error response message without
any action.

If the self-diagnostic function of the slave detects an error, the slave
will return an error response message to all query messages.

The function code of each error response message is obtained by adding
80H to the function code of the query message.
Error code Contents
1 Function code error (An unsupported function code was specified)
2 When the mismatched address is specified.
3

When the specified number of data items in the query message exceeds the maximum number of
data items available

When the data written exceeds the setting range
4 Self-diagnostic error response
(3) No response
The slave ignores the query message and does not respond when:

The slave address in the query message does not coincide with any slave address settings.

The CRC code of the master does not coincide with that of the slave.

Transmission error such as overrun, framing, parity and etc., is found in the query message.

Data time interval in the query message from the master exceeds 24-bit time.
Slave address
Function code
Error code
Error check CRC-16
Error response message