TM 5-6675-318-14
c .
The processor board 4 is the central operating control for the MX 1502 and
contains the Z80 microprocessor, RAM, timing circuits, flag and interrupt logic,
address decoders, and I/O buffers.
The processor board receives data from the dual-
channel satellite receiver board, data entry board, tape controller board, modem
board, alarm clock board, and memory board.
The data is stored in the RAM and is
processed by the processor board.
The results of the processing are supplied to
v a r i o u s b o a r d s .
In power-save operation, the alarm clock board activates the pro -
cessor.
The processor can also be activated by the operator via the keypad. Two
switches on the board select the battery backup protection and memory configuration.
d. The NORM/PROTECT switch is for battery backup protection. The NORM position
battery backup is provided to the entire MX 1502 and is short-term. The PROTECT
position battery backup is provided for memory protection only and is long term.
The EXT/INT switch selects the memory configuration. The EXT position enables the
use of memory chips installed on the memory board.
The INT position enables the use
of memory chips installed on the memory/processor board. The normal operating
condition of the switches will be NORM/PROTECT switch in the NORM position and the
INT/EXT switch in the EXT position.
e. Memory board (3) contains a 52K Read Only Memory (ROM or PROM) and a 6K
Random Access Memory (RAM).
The PROM holds the program required by the processor.
Program data is read into the processor when needed. The RAM is used by the
processor for data storage.
An arithmetic processor chip to speed up the numerical
calculations is also contained on this board.
f. Alarm clock board (D) controls the satellite surveyor during power-save
o p e r a t i o n s.
When in power-save, the alarm clock board maintains two clocks. A time
of day clock and a time remaining clock.
The time of day clock maintains real time
and the time-remaining clock counts down to full power-up condition.
When the
processor has determined the time of the next satellite pass, the time remaining
clock is loaded with the time.
It then powers down all components except the alarm
clock board and the reference oscillator.
When the time remaining clock reaches
zero, all components necessary to process a satellite pass are turned on.
g.
Power to the keyboard is supplied by the alarm clock board to enable the
operator to activate the satellite surveyor to full power by pressing the clear key
( c ) .
The alarm clock board also controls power for overtemperature, lost power, and
other circuits depending on the settings of the front panel switches. The audio
alarm logic is also on this board.
h.
Data entry and display board (a) has three functions - to process input
commands from the keyboard, to transfer data to the display, and to be an
input/output device for RS-232 data.
When a key is pressed on the keyboard, a
signal is sent to an encoder on the data entry and display board and then stored in
a buffer until the processor acknowledges a flag. The data entry logic is then
transferred to the processor.
Output data is stored in buffer on the data entry and
display board and gated to a RAM to provide proper driver signals to the display
o u t p u t c o n t r o l a n d t i m i n g c i r c u i t s .
The driver signals sent to the display register
and buffers on the front panel display card are formatted and level shifted to drive
the alphanumeric fluorescent display.
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