Raytheon Pathfinder 1200 Instruction Manual page 69

6-4
4) Buffer Memory
The buffer memory stores the video data of 3 successive transmissions. A single
transmission of video data is stored into 112 memory cells.
5) Interference Rejecter
The stored transmissions of video data from the buffer memory is serially fed
into the interference rejector. Interference in the video data will be rejected using
pulse correllation techniques.
6) Video RAM
The Video RAM is the main memory for the display. The display area on the
CRT screen is divided by 224 x 224 dots, the Video RAM used in the 1200 Radar
has 65,536 memory cells (256 x 256). '
7) Gate Generator
The gate generator produces a waveform whose duration depends on the setting
of the RANGE switches. The output gate is fed to the sampling clock oscillator.
8) Sampling Clock OSC
The sampling clock oscillator produces the sampling clock pulse, (17.5 MHz)
which is the sampling frequency of 0.25 and 0.5 nm ranges.
9) Count Down
The count down circuit produces the sampling clock pulses for the remaining
ranges (1 to 12 nm ranges). The countdown circuit consists of four divided by 2
circuits and one divided by 3.
10) Sampling Clock Select
The sampling clock select circuit selects the proper sampling clock pulse rate via
the range data signal from the control circuit PCB. The output is fed to the R/W
clock select circuit.
11) R/W Clock Select
The read/write clock select circuit selects either the pulses from the sampling
clock pulse or the display clock pulses of H. counter depending on the appropriate
timing of sampling or displaying. The output is fed to the buffer memory address
counter.
12) Memory Address Counter
The memory address counter produces the buffer memory address data and
controls reading and writing of the buffer memory.
13) W Pulse Generator
The W pulse generator produces the writing pulses to the Video RAM from the
output of the X address counter.
14) Parallel-Serial Converter
The parallel-serial converter circuit changes the four bits data of the Video RAM
to the serial data.