Varec 4000 manual Coded Data, Packed Bit Data

Modbus Implementation Tank Gauge Transmitter

9.5.4Coded 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.

Host Request

Address	Function	Start Reg	Start Reg	# of Reg	# of Reg	Error
	Code	H	L	H	L	Check
01	03	00	14	00	01	XX
ATT Response
Address	Function	Byte	Data	Data	Error
	code	Count	MSB	LSB	Check
01	03	02	00	02	XX

•Hexadecimal representation 0002 (decimal 2)

•Level unit table representation: FT-IN-16TH

9.5.5Packed 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.

Host Request

Address	Function	Start Reg	Start Reg	# of Reg	# of Reg	Error
	Code	H	L	H	L	Check
01	03	00	05	00	01	XX
ATT Response
Address	Function	Byte	Data	Data	Error
	code	Count	MSB	LSB	Check
01	03	02	00	01	XX

Note! Bit #0 is ON indicating a critical low level Alarm

50 Installation and Operations Manual