Banner SureCross DX80 Wireless Networks - Manual (Page 40)

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Banner Engineering Corp. • Minneapolis, MN U.S.A.
www.bannerengineering.com • Tel: 763.544.3164
SureCross Wireless Network
Product Manual
Message Codes
Default Output Conditions
The timeout structure of the DX80 system sets relevant outputs to user-defined conditions
when radio or host communications fail. If the timeout features are enabled, the outputs
are set to default conditions or the last known state before the error. The timeout error
conditions are cleared by either a reset command sent from the host, by using the front
panel display, or by using the auto-recover feature on the DX80. Communications timeouts
occur in three areas within the DX80 system:
• Host Link Failure to the DX80 Gateway device (Modbus Timeout)
• Gateway Link Failure with any Node device
• Node Link Failure with the Gateway
Host Link Failure
A host link failure is detected when the defined timeout period has elapsed with no
communications between the host system (or Modbus master device) and the DX80
Gateway, typically set to four seconds.
The Gateway places an error code in the Gateway I/O 8 register and sends a message to
all relevant Nodes within the system to set outputs to the user-defined default states. Each
Node has an enable flag for a host link failure condition. If the Node’s ‘host link failure’ flag
is not set, the outputs on this Node are not affected.
In the example shown, a host link failure between the host system and the Gateway would result in the outputs of Node 1 and Node 2 sent to
the defined conditions if both Nodes have the host link failure checkbox selected.
Gateway Link Failure
Gateway link failure and Node link failure conditions are determined by three global
parameters, ‘Polling Interval’, ‘Maximum Missed Message Count’ and ‘Re-link Count.’
The Polling Interval defines how often the Gateway communicates with each Node to verify
the RF link is operating. The Gateway increments a Node’s missed message count if a
Node does not immediately report back from a polling request. If a Node’s missed message
count exceeds the ‘Maximum Missed Message Count,’ the Gateway generates a timeout
error in the Modbus I/O 8 register of the appropriate Node.
The auto-recover feature uses the ‘Re-link Count’ parameter. If enabled, the error condition
heals itself if the Gateway to Node communications have successfully exchanged N-number
of good polling messages. The N-number is the ‘Re-link Count,’ or the number of messages
required to re-establish a RF link.
When the Node’s ‘Gateway Link Failure’ flag is set and the Gateway determines a timeout
condition exists for a Node, any outputs linked from the failing Node are set to the user-
defined default state. Each Node has a ‘Gateway Link Failure’ flag that can be set or
vcleared depending on the particular application.
In the sample system shown, the communication link between the Gateway and Node 1
has failed. Node 2 must have its ‘Gateway Link Failure’ flag set to allow its outputs that are linked to Node 1 are set to the defined default state
when the communication link between Node 1 and the Gateway fails.
Host System
Node 1
Node 2
Gateway
Host Link Failure
Host System
Node 1
Node 2
Gateway
Gateway to Node Link Failure