User Manual of A90 Series Inverter
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(Remote Terminal Unit) message, and end tag.
≥3.5 characters
Start
8 digits
Address
8 digits
Function
code
N*8 bits
Data
2*8 bit
CRC check
≥3.5 characters
End
RTU message
PDU
2*8 bit
Address
of
register
2*8 bit
Number
of
registers
2 * number of registers *
8 bits
Register content
Fig. 0-1 Schematic Diagram of Message Frame in RTU Mode
The RTU message includes the address code, PDU (Protocol Data Unit) and CRC[3
check. The PDU includes the function code and data part (mainly including the register
address, number of registers, register content and the like; the detailed definitions of
function codes are different, as shown in 0 Function code).
[3]: the low byte of CRC check is in front of the high byte.
12.3.2 Address code
Address Range
Purpose
1 - 247
Slave
0
Broadcast
12.3.3 Function code
The classification of MODBUS function codes is shown in Fig. 0-2.
