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LonBridge Server User’s Guide 51

Figure 6. Attribute Information for the SNVT_switch_2 Type

The first piece of information that you need about a network variable is its size.

As the figure shows, the SNVT_switch_2 type is a structured type. Thus, you

need to determine the lengths of each of the network variable fields within the

structure to determine the overall network variable size:

• The switch_state_t type is a one-byte enumeration type

• The union includes unsigned short types and the SNVT_multiplier_s type

(which is also an unsigned short type); the Neuron C language defines the

unsigned short type as a one-byte type

• The final member of the structure is an unsigned short, which is 1 byte

Thus, the overall size of the SNVT_switch_2 type is 3 bytes.

The indices for each of the three fields within the network variable are 0, 1, and

2, and each field has a length of 1 byte. For the simplified Lamp Module, the

nviValue and nvoValueFb network variables use fields 0 and 1, but not field 2.

By default, the first value within the setting union scales its values by 0.5, as

shown on the Scales tab in

Figure 7 on page 52.

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