Rockwell Automation 57C570 AutoMax PC3000 User Manual - Manual (Page 192)

18Ć10
RESET
DROP_STATUS_
FROM_NETWORK FAULT_STATUS
FAULT_STATUS
Figure 18.3 Ć Examining Network Status
DROP_STATUS can be either the drop 0 status bit in the slave drop
or the particular drop's status bit in the master. RESET indicates a
manual reset under operator control. When the drop goes offline for
the 120 ms period, the FAULT_STATUS coil will go high and stay
high until it is manually reset by the operator.
18.5 Detecting Partial Network Failure
Recall that all data is broadcast, i.e., transmitted simultaneously to
all drops. If a response is not received from a targeted drop, the
master will retry three times to communicate with that drop.
However, if a drop that was not targeted for that transmission did not
receive the message correctly, the master will not retransmit the
message unless the targeted drop also did not receive it. It is
possible, therefore, that this drop will not contain the most current
copy of the data.
This problem can be detected by monitoring status registers 15Ć18
in the drop 0 area of the module. If these values increase rapidly
over a short period of time, there is a problem with network integrity.
If this is a concern in your application, you should direct data from
slave to master to slave. For example, assume data from one rack
(drop 1) is critical to the operation of another rack (drop 2). After this
data is transmitted to the master, the master can transfer it to its
drop 2 area and then transmit it directly to drop 2.
18.6 What to Do Next
Refer to chapter 19 to help you troubleshoot the PC3000.