Simple all-digital frequency multiplier for ratios between 1 and 2

Discuss hardware-related topics, such as development cartridges, CopyNES, PowerPak, EPROMs, or whatever.

Moderators: B00daW, Moderators

Post Reply
Posts: 10068
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Simple all-digital frequency multiplier for ratios between 1 and 2

Post by lidnariq » Wed Jul 29, 2020 5:24 pm

When I was looking into the Channel F schematics, I mentioned a clock multiplier that multiplies the 3.6MHz clock for chroma by 8/7 to generate the pixel clock:
digital-8-7ths-rate-multiplier.png (2.15 KiB) Viewed 5116 times
(This resulting clock isn't uniform, so when divided by 2 again for the pixel clock the pixels shouldn't be uniform width either. Every other column should alternate between 9:14 and 12:14 PAR, averaging out to a PAR of 3:4)

This can easily be generalized to any number of the form 2ⁿ÷(2ⁿ-1) by changing the number of clock dividers, including just 2÷1:
digital-edge-detector.png (1.52 KiB) Viewed 5116 times
Although a simpler design may be preferable for that specific case:
but R·C << 1/f
but R·C << 1/f
hybrid-edge-detector.png (1.27 KiB) Viewed 5116 times
Given other parts or multiple ICs, any ratio of the form 2·n÷(2·n-1) can be made also:
digital-10-9ths-rate-multiplier.png (2.38 KiB) Viewed 5116 times

Post Reply