1260-45 User Manual
EADS North America Defense
Operation 4-1
Test and Services, Inc. © 1993
Chapter 4
OPERATION
Theory of
Operation
The 1260-45 consists of two PCBAs. The larger PCBA, 405043,
contains the VXI LBus interface, as well as half of the relay
matrix and all of the relay drive electronics. The smaller PCBA,
405044, contains the other half of the relay matrix. The boards
are connected by a ribbon cable which connects the relay coils to
the drive electronics. The relay signal lines are not passed
between the two PCB assemblies inside the module. The VXI
interface is described in the Theory of Operation section of the
1260 Series VXI Switching Cards Manual.
There is no connection between the relay and coil signal lines.
They both are arranged into two 4 x 16 matrices on each board.
There are two coils and the associated circuitry for each relay;
one to set the relay, and one to reset it. The latching-type relays'
coils are only energized when their state is to be changed.
Several features have been incorporated into the card to reduce
the time necessary to update the state of the relays on the card.
First, relay coils have been grouped into sets of 16. This
reduces the amount of backplane overhead associated with
communicating an update from the -01 CPU to the individual
switch module. Second, the software in the -01 keeps track of
the state of the relays. Commands are only sent to the card for
the relays that change, rather than for the entire array. This
minimizes the volume of data that must be sent to the card via
the serial, local bus interface.
All of the rows have non-latching relays in series with the signal
line inputs. This causes the row lines to be opened upon power
fail. Upon power up, these relays remain open until after the -01
CPU has reset each relay. When the power-up sequence is
completed, these "guard" relays are closed and the card
functions normally. The guard relays are transparent, and are
not accessible, to the user.
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