User manual - DATA RECORDER SRD-99 and cooperating software
9.
THE MODBUS
PRO
TOCOL HANDLING
Transmission parameters: 1 start bit, 8 data bits, 1 stop bit, no parity control
Baud rate:
selectable from: 1200 to 115200 bits/second
Transmission protocol:
MODBUS RTU compatible
The device parameters and measurement result are available via RS-485 interface, as
HOLDING-type registers of Modbus RTU protocol. The registers (or groups of the registers)
can be read by 03h function, and wrote by 06h (single registers) or 10h (group of the registers)
accordingly to Modbus RTU specification.
9.1.
LIST OF REGISTERS
Register Write
Range
Register description
01h
1
No
see descr.
Measurement result for channel 1 (not considering the decimal point)
Current inputs version range: -9999÷9999
RTD inputs version range:
-1000÷6000
(for °C)
-1480÷11120
(for °F)
Register from 02h
1
to 08h
1
Measurement result for channel 2..8, registry description like for
channel 1 (see registers 01h).
09h
No
0÷0FFFFh
Information about exceeding the allowable measurement range on the
given measurement channel in binary form:
HGFEDCBAhgfedcba
.
Higher(2
nd
) byte
- exceeding upper limit of measurement range
(
H
- channel no 8,
A
- channel no 1).
Lower(1
st
) byte
- exceeding
upper limit of measurement range (
h
- channel no 8,
a
- channel no 1).
1
- exceeding the range,
0
- measurement result within range
0Bh
No
0÷3
Outputs state (binary)
00000000 000000ba
:
a
– output 1
b
- output 2
0
– open;
1
– closed
11h
Yes
0÷1
"
Backlight
" parameter in "
Display options
" menu:
0
- permanent,
1
- temporary
12h
Yes
0÷20
LCD backlight brightness
13h
Yes
0÷20
LCD contrast
14h
Yes
0÷3
"
Language
" parameter:
0
- Polish,
1
- English,
2
- French,
3
- Spanish
15h
Yes
0÷1
“Temperature unit” parameter (RTD version):
0
-
°
C,
1
-
°
F
18h
No
0÷6
Days of the week registry
19h
Yes
2000÷2099
Year registry
1Ah
Yes
1÷12
Months registry
1Bh
Yes
1÷31
Days registry
1Ch
Yes
0÷23
Hours registry
1Dh
Yes
0÷59
Minutes registry
1Eh
Yes
0÷59
Seconds registry
64
