Bronkhorst Modbus slave interface - Manual (Page 17)

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4.3 Response time
This slave device will respond on each valid request from the master within 100ms. This means that the response
timeout setting of the master should be set to a value larger than or equal to 100ms.
4.4 Supported Modbus functions
This section describes the supported Modbus function codes. Refer to [1] for details.
4.4.1 Read Holding Registers (03)
Possible exception responses
Code Name Meaning
02 ILLEGAL DATA ADDRESS in case of reading of non-existing address, or reading a part of a multi
register parameter (float, long, etc)
03 ILLEGAL DATA VALUE in case of reading less than 1 or more than 125 registers
04 SLAVE DEVICE FAILURE in case of reading a write-only register
Warning: the maximum message size for the Read Holding Registers function is 100 bytes at 9600 baud
(200 bytes at 19200 baud and 400 bytes at 38400 baud). When this size is exceeded, corrupted
responses may be received.
4.4.2 Write Single Register (06)
Possible exception responses
Code Name Meaning
02 ILLEGAL DATA ADDRESS in case of writing to non-existing address, or writing to a part of a multi
register parameter (float, long, etc)
04 SLAVE DEVICE FAILURE in case of writing to read-only register
04 SLAVE DEVICE FAILURE in case of writing illegal value to register
4.4.3 Write Multiple Registers (16)
Possible exception responses
Code Name Meaning
02 ILLEGAL DATA ADDRESS in case of writing to non-existing address, or writing to a part of a multi
register parameter (float, long, etc)
03 ILLEGAL DATA VALUE in case of reading less than 1 or more than 123 registers
04 SLAVE DEVICE FAILURE in case of writing to read-only register
04 SLAVE DEVICE FAILURE in case of writing illegal value to register
When one of the written registers raises an exception, the value written to all subsequent registers are discarded
(ignored).
Page 17 Modbus interface 9.17.035