275
ICC
13.4
Ex: BACnet - Modbus (Analog Objects-Registers)
This example exhibits two networks that both use an object value scheme to
exchange data. In this scenario, the database endianness is irrelevant if the data
types are the same for both networks. This example shows communication
between a BACnet network and a Modbus network using two 16-bit analog value
BACnet objects and two 16-bit Modbus holding registers. As shown in Figure
111, the values from the BACnet network are stored into the database with big-
endian byte ordering. Figure 112 shows the values from the BACnet network
being stored into the database with little-endian byte ordering. Regardless of the
byte-ordering scheme used, the two holding registers on the Modbus network
receive the same values. Notice that in both cases, analog values 1 and 2 have
values of 0x1234 and 0x5678, respectively, while holding registers 1 and 2 also
have values of 0x1234 and 0x5678, respectively. The only difference between the
two cases is how the data is being stored internally on the gateway itself.
Figure 111: BACnet - Modbus (Analog Objects & Registers) Big Endian
Figure 112: BACnet - Modbus (Analog Objects & Registers) Little Endian
