Varec 2920 - Integer Data

2920 Float & Tape Transmitter MODBUSAppendix A — MODBUS Implementation
152 Installation and Operations Manual
Note In all of the following communication examples, the error check value is depen-
dent upon the function code and message content.
Integer data
The integer data is a whole number between 0 and the maximum MODBUS integer (inclusive).
The maximum MODBUS integer is a user-configurable variable that is a whole number
between 0 and 65,535 (inclusive). The integer data must also be scaled for each data type by
entering the desired minimum and maximum value. In order for the integer value to be
correctly interpreted, these scaling factors must match the format expected by the host
system.
The following communication example shows the request for one register starting at register
0 (0000 Hex).
For the following example, assume:
• minimum = 1 meter
• maximum = 15 meters
• maximum MODBUS integer = 65,534
Note A formula for converting numbers to scaled integer format is provided below.
Calculating Integer Data
• Hexadecimal representation: 4124
• Decimal equivalent: 16,676
The data returned for data address 0 is 16,676 (4124 Hex). This value must be scaled using the
following formula to give it meaning.
Host Request
Address Function
Code
Start Reg
H
Start Reg
L
# of Reg
H
# of Reg
L
Error
Check
01 03 00 00 00 01 84 0A
2920 FTT Response
Address Function
Code
Byte Count Data
MSB
Data
LSB
Error
Check
01 03 02 41 24 88 0F
4.56 meters