ICC ETH-1000, Инструкция по эксплуатации

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In contrast, Figure 108 shows the effects of configuring the database for big-
endian byte order. Holding registers 1 and 2 again have values of 0x1234 and
0x5678, respectively. However, when the DeviceNet device receiving the input
data from the gateway interprets these values, the resulting pairs of 2-byte values
become 0x3412 and 0x7856, thus receiving incorrect values for holding registers
1 and 2. Note that in both examples, the DeviceNet network data is always
identical, byte-for-byte, to the gateway’s database. For this reason it is important
to configure gateways that use a bag-of-bytes style network, such as the DNET-
1000, to use the same endianness as defined for that network.
Figure 108: Modbus - DeviceNet Big Endian
13.3 Ex: BACnet - DeviceNet
This example is quite similar to the previous one as data is exchanged between
an object-value style network (BACnet) and a bag-of-bytes style network
(DeviceNet). The key difference is that in this example, BACnet Analog Value 0 is
a 32-bit value, as opposed to two 16-bit Modbus registers. Here, the gateway
reads analog value 0 from the BACnet network, stores the data into the
database, and sends the input data onto the DeviceNet network. Figure 109
demonstrates the data flow from the BACnet network to the DeviceNet network
through a gateway configured to use a little endian database. Because the
DeviceNet specification defines multi-byte values within the byte array to be
interpreted as little endian, it is recommended that the database be configured for
little-endian byte order when using DeviceNet. In the example, analog value 0
has a value of 0x12345678. When the DeviceNet device receiving the input data
from the gateway interprets the 4 bytes, the resulting 4-byte value will be
0x12345678, thus successfully receiving the original value of the BACnet analog
value object.