Sierra INNOVA-MASS 241-VTP - Manual (Page 81)

Series 24-HP Instruction Manual Appendix E MODBUS Commands
IM-24-HP E-3
there is an informal register numbering convention derived from the original (now
obsolete) Modicon Modbus protocol specification, and used by many vendors of
Modbus capable products.
Each range of register numbers maps to a unique range of ad-
dresses that are determined by the function code and the register
number. The address is equal to the least significant four digits of
the register number minus one, as shown in the following table.
Registers Function Codes Data Type and Address Range
00001-09999 01, 05, 15 Read/write bits 0000-9998
10001-19999 02 Read-only bits 0000-9999
30001-39999 03, 04 Read-only 16-bit registers 0000-9998
40001-49999 03, 06, 16 Read/write 16-bit registers 0000-9998
Register Definitions
The meter serial number and those variables that are commonly
monitored (mass, volume and energy flow rates, total, pressure,
temperature, density, viscosity, Reynolds number, and diagnostic
variables such as frequency, velocity, gain, amplitude and filter set-
ting) are accessible via the Modbus protocol. Long integer and
floating point numbers are accessed as pairs of 16-bit registers in
the register order selected in the Modbus Order menu. Floating
point numbers are formatted as single precision IEEE 754 floating
point values.
The flow rate, temperature, pressure, and density variables may
be accessed as either the flow meter internal base units or in the
user-programmed display units, which is determined by the pro-
Registers Usage Valid Function Codes
00001–09999 Read/write bits ("coils") 01 (read coils) 05 (write single coil)
15 (write multiple coils)
10001–19999 Read-only bits ("discrete inputs") 02 (read discrete inputs)
30001–39999 Read-only 16 bit registers ("input regis-
ters"), IEEE 754 floating point register
pairs, arbitrary length strings encoded as
two ASCII characters per 16-bit register
03 (read holding registers) 04 (read
input registers)
40001–49999 Read/write 16-bit registers ("holding regis-
ters"), IEEE 754 floating point register
pairs, arbitrary length strings encoded as
two ASCII characters per 16-bit register
03 (read holding registers) 06 (write
single register) 16 (write multiple
registers)