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The Metasys device type for the gateway is VND.
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Because the Metasys N2 protocol specifies strict response timing
requirements, all accessible data objects must be designated as points,
thereby making use of data mirroring.
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Network characteristics selections: not configurable according to the
Metasys N2 specification.
•
Because all transactions are handled locally within the gateway, write data
checking is not available. For example, if a write to an object is performed,
and the write data is out-of-range of the corresponding secondary network
object, no N2 error will be immediately returned. However, the N2 object
will always reflect the network status and data object value. In other
words, if such an out-of-range write is performed, the unsuccessful write
will be detected and the N2 object's value corrected. If COS is enabled for
that object, the correction will be reported to the NCU upon the next COS
poll request.
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The gateway can be configured to perform a specific set of actions for
each AO or BO point when Metasys communications are lost. Metasys
communications are said to be "lost" when the gateway does not receive
any Metasys packets for a specified period of time, causing a "network
timeout". Refer to section 11.2 for more information about configuring
network timeout parameters.
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The gateway's RS485A port can be directly connected to the N2 bus by
using twisted-pair cable connected as shown in Figure 25. Connect the
N2+ wire to terminal "A", the N2- wire to terminal "B", and the cable shield
to terminal "SHLD" on the gateway's terminal block. Although not available
on all devices, it is also recommended to connect a network ground wire
whenever possible. Continue this connection scheme throughout the
remainder of the network. Always connect each unit in a daisy-chain
fashion, without drop lines, star configurations, etc. For further N2 network
wiring requirements and procedures, please refer to the appropriate JCI
network installation documentation.
49
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