COMPONENT MAINTENANCE MANUAL
C17004
34-57-96
Page 33
COPYRIGHT
SEXTANT Avionique 1995
c
(e) Acquisition function
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
µ
p can (read or write) acquire sequentially for the five channels.
(f) Test code function
This function based on instructions supplied by the data bus, pro-
vides checking code outputs switching of the selected channel.
(g) Time function
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
µ
p,
- A 32 kHz clock, controlled by an external quartz (connected to one
of the TS25).
- Monitoring of the backed-up power supply.
(3) 68020 microprocessor and 68882 co-processor
Master co-processor 68020 is connected to digital co-processor 68882.
The operating characteristics are as follows:
-
µ
p 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
NOV 30/97
1997
The document reference is online, please check the correspondence between the online documentation and the printed version.
