From c7a16a174b9ebe398b370b7ac4a6a99d88ac9ac3 Mon Sep 17 00:00:00 2001 From: tilleul Date: Fri, 15 Jan 2021 09:17:33 +0100 Subject: [PATCH] Create apple2_hires.md --- tools/bitmap editor/apple2_hires.md | 11 +++++++++++ 1 file changed, 11 insertions(+) create mode 100644 tools/bitmap editor/apple2_hires.md diff --git a/tools/bitmap editor/apple2_hires.md b/tools/bitmap editor/apple2_hires.md new file mode 100644 index 0000000..276d834 --- /dev/null +++ b/tools/bitmap editor/apple2_hires.md @@ -0,0 +1,11 @@ +# Apple ]\[ hires +## Structure of the hires screen in RAM +The Apple ]\[ has 2 hires pages. One in $2000-$3FFF. The second one in $4000-$5FFF. Each page is thus 8192 bytes long. + +The dimensions of one hires page is 40 bytes wide and 192 lines high. 40x192 = 7680 bytes. 512 bytes are "missing" and in fact not used/displayed. + +The hires screen is divided in 3 sections of 64 lines. Each section is then divided in 8 sub-sections of 8 lines, each itself divided in 8 sub-sub-sections representing the lines themselves. + +To better understand this division, it's easier to POKE bytes into RAM and see what happens. + +A POKE 8192,