T-VIPS CP525 cMux, User Manual

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48 Functional Description
CP525 cMux User’s Manual Rev. 5.20.12 (3944) ID: um_tsmux
Selected service
Service fallback
switch controller
Service A alarm status
Service A port status
Service B alarm status
Service B port status
G
P
I
in
p
u
t
M
a
n
u
a
l
in
p
u
t
Figure 5.15 Service fallback block diagram
• Required alarm level of the other (spare) input to allow switching
• The confirm time for this level (how long to wait before doing a switch)
The required level of the other service needs to be lower than the configured level, e.g. when
configuring the switch criteria for “Critical (6)” main level, the spare input must be on level
“Major (5)” or lower.
Example: A very simple configuration may be to only switch on “Critical (6)” level and require
“OK (1)” level on the spare input.
The switch controller is designed as a state machine that uses two timeout values in order to
avoid regular switching between the two inputs.
A simplified state chart of the controller is shown in 5.16 .
In “auto” state, the switch controller is “armed” and continuously listens to change in the top
level alarm status for each service. For each change event, the controller evaluates the levels and
checks if the switching criteria is met. If the answer is “yes”, the controller does the following:
• If the
confirm_time
is zero, the controller does a switch immediately and jumps to
a
wait
state where it will wait
switch_timeout
seconds before it re-enters the auto
state.
• If the
confirm_time
is larger than zero, the controller jumps to a
wait_confirm
state
to actually confirm that the switch criteria still is met after the configured time. If the
criteria is still met, the controller performs a switch and jumps to the wait state. If the
criteria is no longer met, the controller does no switching and jumps back to the auto
state.