Varec 2920 - Functions and Data Formats

2920 Float & Tape Transmitter MODBUSAppendix A — MODBUS Implementation
150 Installation and Operations Manual
Note Exception: Because the 2920 FTT does not distinguish between inputs and outputs,
function codes 01 and 02 as they apply to bits, and function codes 03 and 04 as they apply
to numeric values refer to the same data registers. For example, either function code 03
or function 04 can be used to read the integer form of the level variable at data address 0.
Note Default communications settings are shown in bold type above.
Functions and Data Formats
The MODBUS data in the 2920 FTT is arranged in integer registers, floating point registers, and
status bits. The assignments for these registers are found at the end of this appendix.
Function codes 03, 04, 06, and 16 are used with integer registers.
Because of the multiple MODBUS hosts available today, the 2920 FTT supports two floating-
point data formats: a two 16-bit register format and a one 32-bit register format. These two
Function
Code
Function Information Type MODBUS Nomenclature
01 Read Bits Read output status
02 Read Bits Read input status
03 Read Integer, Coded, Status word,
Floating point
Read output registers
04 Read Integer, Coded, Status word,
Floating point
Read input registers
05 Write Bits Force single output status
06 Write Integer, Coded, Status word Preset single register
15 Write Bits Force multiple outputs
16 Write Integer, Coded, Status word,
Floating point
Preset multiple registers
65 Read Floating point Read floating point registers
66 Write Floating point Write floating point registers
Configuration Item Valid Entries
(default in bold type)
MODBUS Config-
urable
ViewRTU
Configurable
MODBUS Address 1 to 254 No Yes
Maximum Integer Size Whole number (0 to 65,534)
(default: 9999)
Yes Yes
Integer Scaling Factors Floating point number Yes Yes
Unit Selection Coding list No No
Baud Rate 300, 600, 1200, 2400,
4800, 9600, 19200
No Yes
Parity Odd, Even, None No No