Modbus Parameter Specifications

Table Of Contents
MODBUS ACE V1.00
_______________________________________________________________________________________
ebm-papst Mulfingen GmbH & Co. KG
Bachmühle 2 ·74673 Mulfingen ·Phone: +49 (0) 7938/81-0 ·Fax: +49 (0) 7938/81-110 ·www.ebmpapst.com ·info1@de.ebmpapst.com
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
AM ·Page 9 of 78
Form 1003
CRC L / CRC H
A checksum CRC is formed across the entire telegram.
The polynomial for checksum formation is 1 + x
2
+ x
15
+ x
16
(i.e. XOR operation with 0xA001).
The start value is 0xFFFF.
The low byte of the checksum is transmitted first, then the high byte.
Further information on calculating the checksum can be found in the "MODBUS over Serial Line Specification
& Implementation guide V1.0".
1.2.2 Response from fan
A fan only responds if
It has been addressed with its own address.
No response is transmitted in the case of a broadcast address.
The telegram length is max. 80 bytes.
The correct number of data bytes has been transmitted to permit interpretation of the telegram.
The checksum has been correctly detected.
Start synchronization:
Following completion of the command from the master the fan waits for a silent interval of at least 3.5 bytes
to elapse. Depending on the command and processing time, the interval may also be considerably longer
(until all the requested data are available to the fan)
Address:
The address from the command of the master (i.e. the fan's own address) is repeated
Command:
If the command can be processed, the command code is repeated.
If the command cannot be processed, the fan responds with an exception.
In this case, the MSB is set in the command.
The command byte for the command "Read holding register (0x03)" is then 0x83 for example.
Data:
The number of data bytes and their meaning differ depending on the command.
CRC L / CRC H
A checksum CRC is formed across the entire telegram.
The checksum formation process is the same as the procedure described above for the command from the
master.