DanBoris' Tech Blog

Interesting - 455 pixels per line. That's a familar number to anyone who's worked with NTSC. I'm going to take a guess that there is a similar vertical counter which resets after 262 lines.

 

One question; why is QA looped back to CLKB?

Yes you are correct, the vertical counter counts to 262 lines before reset.

 

The 7493 is a four bit binary counter, but the first stage of the counter is not connected internally to the other three stages. The output of the first stage comes out on QA and the clock for the second stage is CLKB, so they need to be connected together to form the full 4-bit counter.

 

Dan

 

Interesting - 455 pixels per line.  That's a familar number to anyone who's worked with NTSC.  I'm going to take a guess that there is a similar vertical counter which resets after 262 lines.

 

One question; why is QA looped back to CLKB?

Interesting - 455 pixels per line. That's a familar number to anyone who's worked with NTSC. I'm going to take a guess that there is a similar vertical counter which resets after 262 lines.

Hmm - and that's twice the 2600's pixel clock count, so that would mean the 2600 uses pixels that are twice the width of pixels used in Pongs.