Thales NSS 100S-1 Component Maintenance Manual With Illustrated Parts List page 59

(e) Acquisition function
(f) Test code function
(g) Time function
(3) 68020 microprocessor and 68882 co-processor
Master co-processor 68020 is connected to digital co-processor 68882.
The operating characteristics are as follows:
- µp work frequency: 20 MHz or 25 MHz (see 1.C.),
- 32 bit data bus,
- 32 bit address bus.
(4) Unbacked RAM
This memory comprises 4 circuits of 128 K x 8 bits that create as a whole,
a capacity of 128 Kwords of 32 bits.
(5) Backed-up RAM
COPYRIGHT SEXTANT Avionique 1995
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COMPONENT MAINTENANCE MANUAL
The acquisition function receives the following signals:
- Satellite signal (ACQ 0/15), pre-processed in the HF PCB, Z4,
-The code signals, generated by the TS25 code function.
This function performs the following operations:
- Correlation of the coded signal (during transmission) and of the
code, on two channels (either delay advance or delta point) in or-
der to find the non coded signal.
- Generation of the sine and cosine of the thus generated phase,
- Synchronous detection based on carrier frequency digital phase am-
plitude demodulation,
- Keeping a cumulative total with sequential reset, so that the 68020
µp can (read or write) acquire sequentially for the five channels.
This function based on instructions supplied by the data bus, pro-
vides checking code outputs switching of the selected channel.
This function provides a time measurement of a GPS power supply cut,
during which the RPU is powered by the backed-up power supply
(5VSPIL).
The time function comprises:
- A 40-bit asynchronous counter, with self test by the 68020 µp,
- A 32 kHz clock, controlled by an external quartz (connected to one
of the TS25).
- Monitoring of the backed-up power supply.
1997
C17004
34-57-96
Page 33
NOV 30/97