Varec 4000 - Manual (Page 60)

Modbus Implementation Tank Gauge Transmitter
50 Installation and Operations Manual
9.5.4 Coded Data
Coded data represents a table look-up value. Data written to these registers must be a valid table entry. Invalid data
may cause a Configuration Error to occur. The following example shows coded data at data address 20 (0014 Hex)
representing level units. The value 2 (0002 Hex) returned from the ATT corresponds to level units = FT-IN-16TH.
•
Hexadecimal representation 0002 (decimal 2)
•
Level unit table representation: FT-IN-16TH
9.5.5 Packed Bit Data
Packed bits represent 16 individual status bits packed into one register. The status bits have been packed this way for
systems that prefer handling only register information. These bits may also be read or written individually using a bit
command. The bits within the packed registers are grouped by data or function type. The following communication
example of packed bits shows alarm status information at data address 5 (0005 Hex) returned by the ATT.
Note! Bit #0 is ON indicating a critical low level Alarm
Host Request
Address
Function
Code
Start Reg
H Start Reg
L # of Reg
H # of Reg
L Error
Check
01 03 00 14 00 01 XX
ATT Response
Address
Function
code
Byte
Count
Data
MSB Data
LSB Error
Check
01 03 02 00 02 XX
Host Request
Address
Function
Code
Start Reg
H Start Reg
L # of Reg
H # of Reg
L Error
Check
01 03 00 05 00 01 XX
ATT Response
Address
Function
code
Byte
Count
Data
MSB Data
LSB Error
Check
01 03 02 00 01 XX