[vic20] added vic20 core.

git-svn-id: file:///Users/ces/dev/mist-subversion/trunk@731 8578a998-a533-420b-88ed-89baca3f5bf4

bin/cores/vic20/readme.txt

@@ -0,0 +1,19 @@
+This is the MiST port of the vic20 hardware simulation by MikeJ: http://fpgaarcade.com/?q=node/19
+You can read more about it here: http://ws0.org/tag/vic20/
+The source can be found here: https://github.com/wsoltys/mist-cores/tree/master/vic20
+
+Features:
+- pal vic20/vc20 with 16kb ram expansion
+- .prg and .a0 upload from sd card (.a0 needs to be renamed to .prg)
+- scanline support
+- joystick support
+- the double scan can be turned off
+
+Limitations:
+Due to the different memory layout for an unexpanded vs. expanded vic20 currently only 
+programs/games for expanded vics will work. There's no safety checks for games for the 
+unexpanded vic20 so they usual overwrite the screen ram.
+The prg upload expects the start address in the first two bytes as usual. the rom upload
+via osd expects cartridge roms with the auto start sequence.
+A few glitches are visible. I don't know if its due to my changes or were already in the original
+core.