Sierra Video VS User Manual download pdf (Page 27)

THEORY OF OPERATION

Preferred Master Switch

A requirement of both processors in a two processor (redundant) system is that they are set so

that one is the preferred master processor and the other is the preferred standby processor. This

setting determines which processor will become the master processor when both processors are

powered on at the same time. The setting is made with DIP switch S1-1.

It is essential that S1-1 be set differently on the two processors. Furthermore, it is recommended

that the processor in the uppermost or leftmost slot be the one with S1-1 on (default Master), and

the processor in the lowermost or rightmost slot be the one with S1-1 off (default Slave).

Summarizing:

Processor Slot Recommended S1-1 Setting;

Top or Left ON (default Master)

Bottom or Right OFF (default Slave).

Note:

If S1-1 is set to the same setting on both processors, the router will not function properly.

It is important to know that the setting of S1-1 only determines which processor is the master and

which is the standby immediately following power-up. Later on, the standby processor may have

taken over as master processor, in which case the setting of S1-1 will no longer indicate which

processor is the master.

The current master processor turns on its LEDa, and the standby processor turns it off. So, only

one of the two LEDa’s should be lit at one time, expect during the Boot process

Always look for the processor with LEDa on, and know that it is the current master processor in

control of the router.

Processor Synchronization

The usual state of affairs regarding the redundant processors is that both processors always

power up at the same time, and continue to operate until powered down. In that situation, the

standby processor always is up-to-date with regard to any router configuration information that

the master processor has received. (crosspoints, salvos, panel settings, input/output/level names,

etc.) If the standby processor has to take over as master, it has all the information it needs to do

so.

This usual state of affairs may not always be the case, however. If one processor is removed

from the router for some time, it will no longer have the same router configuration information as

the processor that is running in the frame as master. When this happens, it is important that the

two processors “resynchronize” their configuration information as soon as the processor is put

back in the router. Resynchronization involves the transfer of a considerable amount of

configuration information from the current master processor to the standby processor. If the

standby processor becomes master before the synchronization process is finished, the router

may be running with outdated configuration information.

During the synchronization process, the Yellow LEDs are flashed. When it stops flashing,

synchronization is complete. Complete synchronization may take up to ten minutes. The

synchronization process is always done at power-up.

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Sierra Video VS User Manual Page 27