Sinee EM500 - 12.3 PROTOCOL FORMAT

EM500 Open-Loop Vector Control Inverter User Manual
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12.3 Protocol Format
12.3.1Message Format
As shown in Figure 12-1, one standard MODBUS message includes start mark, RTU
message (Remote Terminal Unit) and end mark.
Figure 12-1 RTU Message Frame
RTU message includes address code, PDU (Protocol Data Unit) and CRC[3] Parity.
PDU includes the function code and data (mainly including register address, register
number and register content; all function codes have different definitions, see the function
code 12.3.3).
[3]: CRC parity, with the low byte in the front and the high byte in the back.
12.3.2Address Code
Address Scope
Purpose
1 - 247
Slave
0
Broadcast
12.3.3Function Code
MODBUS function code classification is shown in Figure 12-2.
Figure 12-2 MODBUS Function Code Classification