VEGA VEGACOM 557 Modbus protocol - Manual (Page 39)

VEGACOM 557 Modbus 39
Data transmission with Modbus RTU
Start
Slave
ad-
dress
Func-
tion
code
Address of
1. register bit
Number of
register
bits
Error
Check
End
Number
of Bytes
Value
range
Meaning
Structure of the enquiry acc. to switching status from Modbus-Master to VEGACOM 557
RTU enquiry telegram acc. to switching conditions (function code 01)
3 ... 4 1 1 2 2 2 3 ... 4
Closed level 1 .. 247 01 0 ... 65.509 8 ... 2.040 CRC Closed level
0x01 0x01 0x00 0x20 0x00 0x20 0xXX 0xXX
Start
Slave
ad-
dress
Func-
tion-
code
No. of
data
bytes
Error
Check
End
No. of
Bytes
Value
range
Meaning
Structure of the answer VEGACOM 557 to Modbus-Master
RTU answer telegram (function code 01)
3 ... 4 1 1 1
1 byte for 8
register bits
2 3 ... 4
Closed level 1 .. 247 01 255 1 ... 127 CRC Closed level
0x01 0x01 0x04 0x00 0x0F 0x00 0x0F 0xXX
Data (switching status)
0xXX
Switching status to
AR card #4
Switching status to
AR card #3