15 Serial Interfaces
SF910i has one MODBUS serial communication channel. SF910i is a “slave” station,
and this means that it never sends messages if not requested to do so by a master
station, so it only sends replies when receives requests addressed to it. The replies are
sent on the same channel over which requests are received.
15.1 Physical Level of Communication
The serial communication channels are implemented in hardware using the RS-485
industry de-facto standard. It is a pair of copper wires that carry differential signals (D+
and D-) plus a shield and a GND reference. Usually, the bus must be terminated with its
characteristic impedance (120 Ohm).
15.2 MODBUS Protocol
The master to successfully communicate with a SF910i configured with the default
parameters must be configured.
Table 15.1: RS-485 Serial Interface Default Settings for MODBUS Protocol
ValueParameter
38400 bpsBaud rate
EvenParity
1Stop bits
8Data bits
1 to 254Addresses
Baud rate on the SF910i must be changed through the local display and touch-buttons.
Stop bits, parity, and data bits are fixed and cannot be modified.
The device address can be changed through Flame Explorer.
8VZZ005286 B 99
15 Serial Interfaces
15.1 Physical Level of Communication
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