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46 lines
1.4 KiB
Plaintext
46 lines
1.4 KiB
Plaintext
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%import string
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%import textio
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%option no_sysinit
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%zeropage basicsafe
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; some bank switching on the C64. See https://www.c64-wiki.com/wiki/Bank_Switching
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main {
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sub start() {
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; copy basic rom to ram and replace ready prompt
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sys.memcopy($a000, $a000, $2000)
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void string.copy(iso:"HELLO!\r", $a378)
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txt.print("8 bytes at $f000 (kernal rom):\n")
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for cx16.r0 in $f000 to $f007 {
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txt.print_ubhex(@(cx16.r0), false)
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txt.spc()
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}
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txt.nl()
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; store some other data in the RAM below those kernal ROM locations
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; switch off kernal rom to see those bytes
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; we cannot print during this time and the IRQ has to be disabled temporarily as well.
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void string.copy("hello !?", $f000)
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sys.set_irqd()
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c64.banks(%101) ; switch off roms
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ubyte[8] buffer
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sys.memcopy($f000, &buffer, 8)
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c64.banks(%111) ; kernal rom back on
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sys.clear_irqd()
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txt.print("8 bytes at $f000 (ram this time):\n")
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for cx16.r0L in buffer {
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txt.print_ubhex(cx16.r0L, false)
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txt.spc()
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}
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txt.nl()
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; we can switch off the basic rom now, but this is not persistent after program exit
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c64.banks(%110)
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; ...so we print a message for the user to do it manually to see the changed prompt.
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txt.print("\ntype: poke 1,54\nto switch off basic rom :-)\n")
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}
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}
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