The main CPU has a dedicated flash ROM that contains the operating system for
instrument control. Front panel settings are stored in
SRAM,
with a battery
providing at least 5 years of backup storage when external power is off.
Main RAM
The main RAM (random access memory) is shared memory for the CPU and the
digital signal processor. It stores the raw data received from the digital signal
processor, while additional calculations are performed on it by the CPU. The
CPU reads the resulting formatted data from the main RAM and converts it to
GSP commands. It writes these commands to the GSP for output to the analyzer
display.
EEPROM
EEPROM (electrically-erasable programmable read only memory) contains
factory set correction constants
unique
to each instrument. These constants
correct for hardware variations to maintain the highest measurement accuracy.
The correction constants can be updated by executing the routines in Chapter 3,
“Adjustments and Correction Constants.
n
Digital Signal Processor
The digital signal processor receives the digitized data from the A10 digital
IF. It computes discrete Fourier transforms to extract the complex phase and
magnitude data from the 4
kHz
IF signal. The resulting raw data is written into
the main RAM.
Al8 Display
The Al8 display is an 8.4 inch LCD with associated drive circuitry. It receives a
+3.3
V power supply from the A19 GSP, along with the voltage generated from
the A27 backlight inverter. It receives the following signals from the A19 GSP:
n
digital
TTL
horizontal sync
w
digital
TTL
vertical sync
n
blanking
w
data clock
n
digital
‘ITL
red video
n
digitalTI’Lgreen
video
n
digital
‘ITL
blue video
Theory of Operation 12-11
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