Modbus Parameter Specifications

MODBUS ACE V1.00
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DocNo.: 634505DocNo: 446144DocNo.:358982DocNo.:322523DocNo.:309753DocNo.:303997DocNo.:276241DocNo.:256078DocNo.:196392 ·Template: 2 dated 10/6/2003 ·File: ext001931381.docx ·Last printed 9/30/2019 10:29:00
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Form 1003
1.3 Commands
1.3.1 Read holding register
Command code: 0x03
The content of several holding registers can be read out with this command.
Holding registers are parameters for which both read access and write access exist
Command from master:
4 data bytes are transmitted:
 1. Holding register address MSB
 1. Holding register address LSB
 Number of addresses to be read MSB
 Number of addresses to be read LSB
The holding registers will be described later.
Response from fan:
The following data bytes are transmitted:
 Byte count (number of addresses to be read * 2)
 Data of 1st holding register MSB
 Data of 1st holding register LSB
Optional:
 Data of the following holding registers (0..n)
Exception codes:
Just one data byte (exception code) is transmitted in the event of an error
Exception codes:
0x02: The permissible range of the holding registers D000 ... D614 has been exceeded
0x03: The maximum telegram length for the response (80 bytes) has been exceeded,
i.e. more than 37 holding registers or 0 holding registers were requested.
0x04: A holding register cannot be read on account of a fault in the electronics