5.1.2 Communication Format
Baud rate : 2400, 4800, 9600, 19200
Low level character format :
With Odd or Even parity = 1 start bit, 8 data bits, 1 parity bit,
1 stop bit
With NO parity = 1 start bit , 8 data bits, 2 stops bits.
5.1.3 Modbus Format
Data format :
RTU
32 bit, floating point format to IEEE-754 standard, exponent
bias 127, most significant byte transmitted first. There is no
word reversal.
Address range: 1-247
Error Check :
Cyclic Redundancy Check (CRC), Polynomial exclusive
OR value A001h Low byte sent first.
5.3.5 Modbus Protocol
Only the RTU (Remote Terminal Unit) form of the Modbus
protocol will be supported and all references in this sheet
refer to RTU format.
Typically, the master or controller requests data from its
slaves by polling them one at a time and waiting for a
pre-defined amount of time for a response. If a node
doesn't respond within this time period the master will try
accessing it a further two times before indicating to the
Scada system that the node has gone off-line or there is a
fault with it. If all is well the node will respond with the
data requested.
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