Chapter 4 - Principles of Operation
The Operator/Remote Interface Assembly contains the microprocessor, up to
512 kbytes ROM, 64 kbytes RAM, and 64 kbytes NVRAM. A Motorola
MC68881 mathematical coprocessor is optionally installed on the ORI board
to process mathematical algorithms.
The assembly has 16 analog input channels. Each channel is served by a 12-
bit analog-to-digital converter for data acquisition. The input stage of the
analog-to-digital converter is configured to accept signals in the ±10V dc
range.
The assembly has 16 TTL auxiliary inputs and 16 TTL outputs.
The assembly is equipped with three fast serial links for communication.
Serial link one is dedicated to communication with the servo board; link two
is dedicated to communication with the system controller. Media is
selectable: fiber optics, twisted pair with multidrop capabilities (RS-422/485),
RS-232, or IEEE-488. Host interface is 9600 baud: ORI to servo board is 100
kbaud.
The assembly's firmware provides the board with built-in testing. Startup
self-test functions include RAM write/read test, NVRAM checksum, and
DAC/ADC loopback test.
4.2.4 Autotrack Assembly (Optional)
The Autotrack Assembly option (Figure 4.6) is used in tracking applications
to allow the system to follow a moving target based on error information
derived from a tracking feed. The Autotrack Assembly is equipped with a
Motorola 68302 microprocessor and provides scanning signals to the tracking
feed for modulation of difference signal information (tracking video) onto the
data signal. The assembly also demodulates the tracking video from the
tracking receiver to generate axis position errors for use in positioning the
pedestal and antenna. The demodulated errors from the Autotrack Assembly
are sent to the servo board, via the backplane serial interface, every 20
milliseconds. The assembly has the capability of receiving inputs from up to
seven receivers simultaneously.
The Autotrack Assembly contains the microprocessor, up to 512 kbytes ROM,
64 kbytes RAM, and 64 kbytes NVRAM.
The assembly has 16 analog input channels. Each channel is served by a 12-
bit analog-to-digital converter for data acquisition. The input stage of the
analog-to-digital converter is configured to accept signals in the ±10 V dc
range.
The Autotrack Assembly has feed and scanner control with TTL differential
drivers which are compatible with ViaSat Satellite Networks ESCAN and
MONOSCAN tracking feeds.
3862 Autotrack Controller
4-11
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