10-05-2022, 01:24 PM
The microbee was originally released with a 12MHz pixel dot clock which was subsequently increased to 13.5Mhz to add 80 column support on a standard composite video signal.
A way to detect the difference between the dot clocks is by peeking at the CRTC configuration table in the BASIC or BOOT ROM.
A side effect of the dot clock increase is the pixel aspect ratio becoming narrower.
From this dot clock, all video formats are derived and you're free to choose existing ones or create your own.
Just remember to ensure that the chosen video format is compatible with the microbee keyboard scanning.
Just as a guide, if you look through the forum, the microbee is also capable of the 32x24 colour screen as used by the ZX Spectrum, the 256 x 224 format of the Space Invaders Arcade machine, MSX text and graphics modes & Amstrad CPC text/graphics modes including 160x200, 320x200.
A way to detect the difference between the dot clocks is by peeking at the CRTC configuration table in the BASIC or BOOT ROM.
A side effect of the dot clock increase is the pixel aspect ratio becoming narrower.
From this dot clock, all video formats are derived and you're free to choose existing ones or create your own.
Just remember to ensure that the chosen video format is compatible with the microbee keyboard scanning.
Just as a guide, if you look through the forum, the microbee is also capable of the 32x24 colour screen as used by the ZX Spectrum, the 256 x 224 format of the Space Invaders Arcade machine, MSX text and graphics modes & Amstrad CPC text/graphics modes including 160x200, 320x200.