mirror of
https://github.com/irmen/prog8.git
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86 lines
2.0 KiB
Lua
86 lines
2.0 KiB
Lua
%target c64
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%import syslib
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%import textio
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%zeropage basicsafe
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%option no_sysinit
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; Create a custom character set on the C64.
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main {
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sub start() {
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txt.color(1)
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txt.print("creating charset...\n")
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charset.make_custom_charset()
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; activate the new charset in RAM
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ubyte block = c64.CIA2PRA
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const ubyte PAGE1 = ((c64.Screen >> 6) & $F0) | ((charset.CHARSET >> 10) & $0E)
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c64.CIA2PRA = (block & $FC) | (lsb(c64.Screen >> 14) ^ $03)
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c64.VMCSB = PAGE1
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txt.print("\n @ @ @ @\n")
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}
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}
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charset {
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const uword CHARSET = $2000
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sub copy_rom_charset() {
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; copies the charset from ROM to RAM so we can modify it
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sys.set_irqd()
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ubyte bank = @($0001)
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@($0001) = bank & %11111011 ; enable CHAREN, so the character rom accessible at $d000
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sys.memcopy($d000, CHARSET, 256*8*2) ; copy the charset to RAM
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@($0001) = bank ; reset previous memory banking
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sys.clear_irqd()
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}
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sub make_custom_charset() {
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copy_rom_charset()
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; make all characters italic
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ubyte c
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for c in 0 to 255 {
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uword ptr = CHARSET + c*$0008
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@(ptr) >>= 2
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@(ptr+1) >>= 2
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@(ptr+2) >>= 1
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@(ptr+3) >>= 1
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;@(ptr+4) >>= 0
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;@(ptr+5) >>= 0
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@(ptr+6) <<= 1
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@(ptr+7) <<= 1
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ptr = CHARSET + 256*8 + c*$0008
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@(ptr) >>= 2
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@(ptr+1) >>= 2
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@(ptr+2) >>= 1
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@(ptr+3) >>= 1
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;@(ptr+4) >>= 0
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;@(ptr+5) >>= 0
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@(ptr+6) <<= 1
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@(ptr+7) <<= 1
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}
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; add a smiley over the '@'
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ubyte[] smiley = [
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%00111100,
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%01000010,
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%10100101,
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%10000001,
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%10100101,
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%10011001,
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%01000010,
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%00111100
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]
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sys.memcopy(smiley, CHARSET, len(smiley))
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}
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}
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