Initial commit: C64 project skeleton with oscar64 submodule

2026-07-17 00:36:14 +02:00
commit cbe5cf6a47
31 changed files with 29332 additions and 0 deletions
@@ -0,0 +1,56 @@
+# VIC-II (Video Interface Chip II)
+
+Source: https://www.c64-wiki.com/wiki/VIC
+
+## Identification
+
+VIC-II is the video chip used in the C64 / C128 family. There are two VIC-II types in the C64: the 6567 in NTSC machines and the 6569 in PAL machines. Newer C64 versions use the functionally equivalent 8562 (NTSC) and 8565 (PAL) chips.
+
+## Features
+
+- 16 kB address space for screen, character and sprite memory
+- 320 × 200 pixels video resolution (160 × 200 in multi-color mode)
+- 40 × 25 characters text resolution
+- Three character display modes and two bitmap modes
+- 16 colors
+- Concurrent handling of 8 sprites per scanline, each of 24 × 21 pixels (12 × 21 multicolor)
+- Raster interrupt
+- Smooth scrolling
+- Independent dynamic RAM refresh (an unusual feature for a graphics processor)
+- Bus mastering for a 6502-style system bus; CPU and VIC-II accessing the bus during alternating half-clock cycles (the VIC-II will halt the CPU when it needs extra cycles)
+
+## Memory Addresses of the VIC-II
+
+| Hex Address | Dec Address | Page | Contents |
+|-------------|-------------|------|----------|
+| $D000-$D3FF | 53248-54271 | Page 208-211 | VIC-II registers |
+| $D800-$DBE7 | 55296-56295 | Page 216-219 | Color RAM |
+
+- Sprites lie at address MEM(Start of screen mem + $03F8 + sprite number)*64
+- The start of the Screen RAM is set by $DD00 (the VIC bank, see CIA 2) and $D018.
+
+## Technical Notes (from Christian Bauer's article)
+
+The operation of the VIC-II is thoroughly described in the document
+"The MOS 6567/6569 video controller (VIC-II) and its application in the Commodore 64"
+by Christian Bauer. See `vic/cebix-vic-article.txt` for the full text.
+
+Key facts:
+- The cycle count starts at 1; for example, VICE starts counting at 0.
+- Writing to $D011/$D012 can immediately trigger a raster IRQ, provided no raster IRQ has yet been triggered in the current line.
+- The vertical "expansion flip-flop" is somewhat misleadingly named; its state actually indicates whether a line in the sprite data should currently be skipped or not.
+- VCBASE and MCBASE are used to reset VC and MC to their initial values.
+- VMLI is not a pointer but rather a 40-bit shift register that controls the 40 enable bits of the VIC-II's internal "40×12 bit video matrix/color line."
+
+## Known Variants
+
+- MOS 6560 / 6561: VIC-I (VIC-20)
+- MOS 6566: VIC-II for MAX Machine
+- MOS 6567: VIC-II for (NTSC) C64
+- MOS 6569: VIC-II for (PAL) C64 (R1/R3/R4/R5)
+- MOS 6572/6573: VIC-II (PAL-N/PAL-M)
+- MOS 8562: VIC-II (NTSC) for later C64 / C128
+- MOS 8564/8565/8566/8569: VIC-II variants for C64 / C128
+- CSG 4567: VIC-III (C65/C64DX)
+
+The NMOS variants 6566/67/69 require +12V on Pin 13/Vdd; the HMOS-II variants (8562/65) require only +5V DC. The 856x variants exhibit the "Grey Dots" problem.