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COM port USB (RS-232), configuration parameters
Baud rate
Parity
Data Bits
Stop bits
Flow Control
A.3 Modbus transactions
The master issues a Query Modbus frame on the bus. The addressed salve answers (except for
broadcast requests) with a Response Modbus frame. The salve answer can be a correct answer
or an Exception in case of error.
For better data throughput, Sylvac modules always use the RTU transmission mode.
For more details on Modbus protocol, refer to the MODBUS Application Protocol.
www.modbus.org/docs/Modbus_Application_Protocol_V1_1b.pdf.
A.4 Frame description
Query frame format
Address field (8 bits)
Where :
Address field :
The slave number (1...247 , 0=reserved for broadcast)
Function code :
See following table for supported D30Xy functions
Error check (CRC) : Based on polynome 1 + X2 + X15 + X16
Normal response frame format
Function code (8 bits)
Exception response frame format
Function code + 0x80 (8 bits)
4'800...256'000 bds (transmission speed, default = 19'200 bds)
Even
7
2
None
Function code (8 bits)
ADU (Application Data Unit)
PDU (Protocole Data Unit)
Data (any bits)
Exception code (8 bits)
Data (any bits)
59
Error check (CRC) (16 bits)
Error check (CRC) (16 bits)
Error check (CRC) (16 bits)
A
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