The heart of Pong, and any of the discrete logic games is the horizontal and vertical counter. These counters continuously step through each horizontal and vertical position on the screen. The output of the counters is fed to all the other logic of the game which ultimately determines if each pixel should be on or off (or what color it should be in the case of color graphics).

Everything begins here

This is the main clock generator in Pong. The crystal (which is 14.318 MHz although it’s not labeled on the schematic), along with the two inverters, two resistors and two capacitors form the main oscillator. The output of the oscillator goes into E6 which is wired as an inverter. E6 buffers the clock signal so the oscillator doesn’t get loaded down by the next chip, and it also helps square up the clock a little bit. Next the clock goes into a J/K flip-flip which is wired in toggle mode. The flip-flop finishes squaring up the clock signal and also divides the frequency in half so CLK will be approximately 7 MHz.