User manual - RATEMETER STI-94
2
- these registers are active only if device is equipped with current or voltage output
3 - after writing to register no 20h the device responds witch an “old” address in the message.
4
- after writing to register no 22h the device responds with the new baud rate.
5
- the value of the “
mbAccE
” 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.
11.2.
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 5).
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:
“mbAccE”
parameter)
11.3.
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) and status, the device address = 01h:
ADDR
FUNC
REG H,L
COUNT H,L
CRC L,H
01
03
00
01
00
03
54
0B
The answer :
ADDR
FUNC BYTE C
DATA H1,L1
DATA H2, L2
DATA H3.L3
CRC L,H
01
03
06
00
01
86
A0
00
00
2A
B4
DATA H1, L1 - reg. 01h (1 - high word of measurement value)
DATA H2, L2 - reg. 02h (86A0h - low word of measurement value ),
DATA H3, L3 - reg. 03h (0 - measurement status).
In this example measurement value is equal 186A0h (100 000 in decimal format).
Decimal point position is not included in measurement value (reg. 01h and 02h).
Decimal point position can be read from reg. 04h (
“
PrEc
”
parameter).
45
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