13
EN
COUNTIS E43/E44 - 547981A - SOCOMEC
8.3. Communication structure
The device communicates via a Modbus protocol which involves a dialogue in accordance with a master/slave structure. The
communication mode is the RTU (Remote Terminal Unit) mode with hexadecimal characters composed of at least 8 bits.
Modbus frame structure (master -> slave question):
Slave address Function code Address Number of words to be
read
CRC 16
1 byte 1 byte 2 bytes 2 bytes 2 bytes
To comply with the Modbus protocol, the inter-character time must be ≤ 3 silences.
This means the time for 3 characters to be emitted so that the message is processed by the COUNTIS E43/44.
In order to use the information correctly, you must use the Modbus functions in accordance with the codes:
• 3: to read n words (maximum 128).
• 6: to write one word.
• 16: to write n words (maximum 128).
N.B.:
1 word <=> 2 bytes <=> 16 bits
2 words <=> 4 bytes <=> 32 bits
The broadcast communication is available for the log that stores the tariff.
8.4. Communication tables
The communication tables and relevant notes are available on the COUNTIS E43/E44
documentation page on the website at the following address:
www.socomec.com/en/countis-e4x
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