User manual - METER SRT-457
Register
Write
Range
Register description
55h
Yes
0 ÷ 1
H r2
parameter in
HOLd
menu:
0
-
rEAL
mode ;
1
-
HOLd
mode
56h
Yes
0 ÷ 1
H r3
parameter in
HOLd
menu:
0
-
rEAL
mode ;
1
-
HOLd
mode
57h
Yes
0 ÷ 1
H r4
parameter in
HOLd
menu:
0
-
rEAL
mode ;
1
-
HOLd
mode
2
- after writing to register no 20h the device responds with an old address in the message.
3
- after writing to register no 22h the device responds with the new baud rate.
4
- the value of the
mbAc
parameter is also connected to write to this register, so it is possible to block a writes, but
impossible to unblock writes via RS-485 interface, The unblocking of the writes is possible from menu level only.
8.2.
TRANSMISSION ERRORS DESCRIPTION
If an error occurs while write or read of single register, then the device sends an error
code according to Modbus RTU specifications (example message no 1).
Error codes:
01h
- illegal function (only functions 03h, 06h and 10h are available),
02h
- illegal register address
03h
- illegal data value
08h
- no write permission ( see:
mbAc
parameter)
A0h
- exceed of upper border of input range
60h
- exceed of lower border of input range
A0h and 60h codes can appear only during reg. 01h is reading by 03h function (read of
a single register).
8.3.
EXAMPLES OF QUERY/ANSWER FRAMES
Examples apply for device with address 1. All values are represent hexadecimal.
Field description:
ADDR
Device address on modbus network
FUNC
Function code
REG H,L
Starting address (address of first register to read/write, Hi and Lo byte)
COUNT H,L
No. of registers to read/write (Hi and Lo byte)
BYTE C
Data byte count in answer frame
DATA H,L
Data byte (Hi and Lo byte)
CRC L,H
CRC error check (Hi and Lo byte)
1. Read of the displayed value (measurement), SRT-457 device address = 01h:
ADDR
FUNC
REG H,L
COUNT H,L
CRC L,H
01
03
00
01
00
01
D5
CA
a) The answer (we assume that the measure result is not out of range):
31
