Figure 2 Single Network Break - Secutron MR-2200 Programming Manual

Operation and Programming Concepts
Network Reboot
If a Network Reboot command is initiated at a panel, it is broadcast normally and then the
panel reboots itself. Upon receiving the Network Reboot command, a panel passes the
command on to the next panel and then reboots itself. This has the affect of causing all the
panels to reboot simultaneously.
Network Verify
Network Verify is the process by which the master panel queries the rest of the network to
determine on-line status. Each panel will respond to the network verify request. The user can
also request a Network Verify at any time from any panel in the network.
1.3.3 Network Communications
Information is sent across the network in frames. In addition to the operator generated
frames described above, alarm, supervisory, and trouble frames are sent across the
network whenever a device or panel indicates a problem. There are two types of frames:
specific and broadcast. Specific frames are sent from one unit to another. Broadcast frames
are sent from one unit to all others.
Specific Frames
Specific frames deal with information generated at one panel and required at another. This
type of frame is passed from panel to panel until it reaches its destination. Each panel has a
list as to which port to send frames from to reach all other panels through the fewest number of
panels. Since networks generally have all communications links running at the same baud
rate, this is generally the shortest time as well.
If there is a break in the communications (see Figure 2), the panel that cannot pass the
message on sends it back the way it came. This causes the frame to go the long way around
the network. If there are two breaks in the network loop, the frame is again reversed at the
second break. When the originating panel receives it after the second turn around, the
originating panel realizes there is a major fault in the network and considers the frame to be
orphaned and destroys it. This generates a Network Reboot Required trouble. This is passed
on to all other panels (or at least as many as can be reached). The reason the orphan frame is
destroyed is to prevent unexpected operation when the network is finally repaired, such as a
panel starts ringing its bells because of an alarm from the previous day.
M R 2 9 4 4
M R 2 2 0 0 M R 2 9 0 0
I D # 3
I D # 1 I D # 2
C O M 2 C O M 1 C O M 2 C O M 1 C O M 2 C O M 1
M R 2 2 0 0
M R 2 9 4 4
I D # 5
I D # 4
C O M 1 C O M 2 C O M 1 C O M 2
Figure 2 Single Network Break
Broadcast Frames
Broadcast frames deal with information that affects the entire network. When a broadcast
frame is created by a panel or annunciator, it is sent out both network communications ports.
Each unit in turn receives the broadcast in one port, act upon it and pass it on out the other
port. Upon reaching the unit that generated the broadcast frame, that unit then disposes of it.
This means that under normal circumstances, all units receive a broadcast twice and act upon
it twice.
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