Gantner E Series, Руководство по связи

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e.bloxx Communication
MODBUS PROTOCOL
HB_EBLOXX_COM_E_V12.doc
33
Gantner Instruments Test & Measurement GmbH
5.2. Telegram Format
Request Telegram
Response Telegram
The request and response telegrams in the RTU-mode used by the e.bloxx modules are starting with an idle-interval of
at least 3.5 character length. Most simple this will be performed by waiting for at least 4 character-times (CT) after
receiving the last character of a telegram. The telegrams have no Start-Delimiter and no End-Delimiter too. The first field
after that idle-interval is the ISM-Address (ADR) followed by the function number (FNR) and the function parameters or
data respectively. At the end the telegrams contain a check sum (CRC) with the length of 16 bits. The check sum is
calculated from the whole telegram without the CRC itself. The CRC-polynomial is: u
15
+ u
13
+ 1. The start value is
hex
FFFF.
5.3. Instruction Set
With the MODBUS-protocol the data are read and written via register accesses. The following register accesses are
defined for the communication with the sensor modules:
Function Number Function
03 hex Read holding register (read/write register)
04 hex Read input register (read only register)
06 hex Preset single register
08 hex Diagnostic
10 hex Preset multiple register
Table 5.2 - MODBUS commands supported by the e.bloxx modules
Idle Interval ADR FNR Function Parameters / Data CRC
> 3.5 CT 1 Byte 1 Byte n Byte 2 Byte
Idle Interval ADR FNR Function Parameters / Data CRC
> 3.5 CT 1 Byte 1 Byte n Byte 2 Byte