Model 3095FB Multivariable Transmitter with Modbus Protocol
Modbus Protocol Guide
Page 8 of 79
2.3 Data Types
The transmitter’s mapped addresses store and use data types supported by many Modbus-
compatible PLCs and host controllers. Table 2-2 lists those data types according to their
mapped addresses and corresponding function codes. To increase compatibility with many
different kinds of hosts, the data types have been remapped to several different locations as
shown in Table 2-2. The additional Modbus addresses were implemented in the 3095FB
output board software beginning with Rev.107.
All the registers in this document are referenced to one. The registers in Modbus messages are
referenced to zero. This means the number of the mapped address register (i.e. 0005) is one
higher than the actual number (i.e. 0004) that is sent in the Modbus frame message.
There are a number of 8 bit values that are stored in 16 bit registers. The 8 bit value is stored in
the Least Significant Byte of the 16 bit register. For example the value $24 would be stored as
$0024. This does not apply to ASCII characters which are stored as two characters in each 16
bit register.
Floating point values are stored as single precision IEEE 754 floating point numbers. Since
IEEE 754 floating point numbers are 32 bits long, they must be stored as either two 16-bit reg-
isters or as one 32-bit register. The 3095FB supports both types of floating point registers. See
Section 2.3.1 for a more detailed explanation of the register mapping.
