Rockwell Automation T8017 Trusted Peer to Peer Communications - Manual (Page 10)

Trusted
TM
Communication Software Package T8017
Issue 10 Mar 08 PD-T8017 10
1.1.2. Input Data
When the system receives peer input data, it is validated before it is passed on to the application
program for use.
The system monitors the refreshing of input data. If fresh input data is received within the time-out
period, the input refresh status bit on the input board is set to true. If fresh input data is not received,
this status bit is set to false and the input data will either hold last state or go to the fail safe value
depending on CONTROL rack variable state set by the application. The system always uses the latest
data received (determined by a data sequence number) from all of the subnet links to update the
application. The refresh timer is not updated if data older than the current data is received.
The length of time the system waits for fresh input data is configurable via the refresh time-out
parameter on the input boards.
1.1.3. Output Data
When peer output data is changed by the application program, it is sent to the Trusted TM
communications interface ready for transmission over the peer subnet. Only the latest output data for
a particular peer system is stored on the communications interface. If fresh output data is received
before the previous values have been transmitted, they will be overwritten by the new data.
If the application program has not changed output data within a time-out period, the current values are
sent to the communications interface. This ensures the corresponding input board on the Peer system
expecting the data is kept refreshed.
The length of time the system waits for fresh output data from the application program is configurable
via the refresh time-out parameter on the Peer to Peer output boards.