Version 4.0
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2. Specifications
2.1 Communication Specifications
Item
Specification
Electrical specification
Based on EIA RS-485
Transmit system
2-wire, semi-duplicate
Synchronizing system
Asynchronous mode
Connection format
1 : N
Number connection unit
Up to 255 units
Transmission distance
500m max
Transmission speed
2400 / 4800 / 9600 / 19200 selectable
Start bit
1 bit
Data length bit
8 bits
Parity bit
None
Data format
Stop bit
2 bits
Transmission code
HEX value (MODBUS RTU mode)
Error detection
CRC-16 bits
Isolation
Functional isolation between transmission circuit
and others (with stand voltage: 500V AC).
A typical MODBUS protocol character is shown below:
1
2
3
4
5
6
7
8
9
10
11
Start bit
Data bits
Stop bits
One character is including 1 Start bit and 8 Data bits and 2 Stop bits.