Philips SPENDEX 40 Maintenance Manual page 22

NATO CONFIDENTIAL
S P E N D E X 4 0 U A 8 2 5 1 / 0 0 A N D / O l L I M I T E D M A I N T E N A N C E M A N U A L
4.6
Kev memory board
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4 . 6 . 1 P r o g r a m m e m o r y 2
*
Program memory 2 (U EPROM, 32,768 x 8 bit) contains part of the
firmware.
4 . 6 . 2 Z e r o i s e m e m o r y
The zeroise memory (8192 x 8 bit) is used by the comsec controller
for the storage of key material.
The zeroise memory is fed with the battery voltage, so that in case
of power breakdown its contents remain preserved.
When the ZEROISE push button is pressed or the front panel or upper
cover of the equipment is removed, the contents of the zeroise memory
will be zeroised.
4 . 6 . 3 K e y v a r i a b l e m e m o r y
The key variable memory (8192 x 8 bit) is destined for the storage
of, among other things, the settings of the apparatus.
The key memory is fed with the battery voltage, so that in case of
power breakdown its contents remain preserved.
4 . 6 . 4 Z e r o i s e c i r c u i t
When the ZEROISE push button is pressed or the front panel or the
upper cover of the equipment is removed, the zeroise circuit will be
activated. The zeroise circuit disconnects the zeroise memory from
the battery voltage and the comsec data/control bus, as a result of
which the contents of the zeroise memory will be destroyed and the
zeroise alarm signal ZERAL will be activated.
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4 . 6 . 5 Z e r o i s e s w i t c h
As soon as the upper cover is removed, the zeroise switch is opened,
as a result of which the zeroise circuit will be activated.
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