VEGA VEGACOM 557 Modbus protocol - Manual (Page 44)

44 VEGACOM 557 Modbus
Start
Slave
ad-
dress
Func-
tion
code
Address of
1. register
word
No. of
register
words
Error
Check
End
Number
of Bytes
Value
range
Meaning
Structure of the meas. value enquiry Modbus-Master to VEGACOM 557
ASCII enquiry telegram acc. to measured values (function code 04)
1 2 2 4 4 2 2
: 1 .. 247 04 0 ... 65.509 1 ... 127 LRC CR LF
0
Start
Slave
address
Function
code
No. of
data
b y t e s
Error
Check
End
No. of
Bytes
Value
range
Meaning
Structure of the answer VEGACOM 557 to Modbus-Master
ASCII answer telegram (function code 04)
1
Data (DCS values)
DCS value 1 of
VEGAMET #2:
Status: 0x00
Unit: 0x00
Meas. value:
0x014A
= 3.30%
Data transmission with Modbus ASCII
1 0 4 0 0 1 C 0 0 0 2 : X X CR LF
0 1 0 4 0 4 0 1 4 A : X X CR LF
:
2 2 2 8 (per DCS value) 2 2
1 .. 247 04 2 ... 254 LRC CR LF
0 0 0 0
Procedure with Modbus-Master-simulation (e.g. PC) Procedure with Modbus-Master-simulation (e.g. PC) Procedure with Modbus-Master-simulation (e.g. PC) Procedure with Modbus-Master-simulation (e.g. PC) Procedure with Modbus-Master-simulation (e.g. PC)
In case the data enquiry should be made via a Modbus-Master-simulation, this can be done,
for example, via a self-written communication driver using the "Function code 04 = Read Input
Registers“. The following demonstration should explain the communication processes between
Modbus-Master and VEGACOM 557 on the Modbus.
Example for data from VEGAMET 514:
A DCS value should be collected from VEGAMET #2 (DCS output 1). VEGACOM 557 operates
in mode "Sort measured values acc. to VEGAMET addresses“. The Slave-address of VEGA-
COM 557 is set to 1.
Current meas. value on VEGAMET DCS output 1 is: 3.30% (= 0x014A)