ICON LevelPro ITC 450 Series Quick Start Manual page 21

LevelPro — ITC 450 & 350 Series
®
Tank Level Display + Controller
RS485 Modbus Programming
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 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).
11.3. EXAMPLES OF QUERY/ANSWER FRAMES
Examples apply for device with address 1. All values are represent hexadecimal.
Field description:
ADDR
FUNC
REG H,L
COUNT H,L
BYTE C
DATA H,L
CRC L,H
1. Read of the displayed value (measurement), SRP-N118 device address = 01h:
ADDR
01
a) The answer (we assume that the measure result is not out of range):
ADDR
01
DATA H, L - displayed value = 255, no decimal point.
24-0352 © Icon Process Controls Ltd.
Device address on modbus network
Function code
Starting address (address of first register to read/write, Hi and Lo byte)
No. of registers to read/write (Hi and Lo byte)
Data byte count in answer frame
Data byte (Hi and Lo byte)
CRC error check (Hi and Lo byte)
FUNC REG H,L
03 00 01
FUNC BYTE C
03 02
Decimal point position can be read from reg. 03h.
COUNT H,L CRC L,H
00 01 D5
DATA H,L CRC L,H
00 FF F8
CA
04
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