[WIP] Gamepak unused addresses
Former-commit-id: 7946d38faf49fc0f95aab8654611b94aae443949 Former-commit-id: b3654fd4750d472a20fe5db9de0019d774a4ee61
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@ -82,6 +82,20 @@ impl Cartridge {
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self.symbols = other.symbols;
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self.backup = other.backup;
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}
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#[inline]
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/// From GBATEK:
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/// Reading from GamePak ROM when no Cartridge is inserted -
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/// Because Gamepak uses the same signal-lines for both 16bit data and for lower 16bit halfword address,
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/// the entire gamepak ROM area is effectively filled by incrementing 16bit values (Address/2 AND FFFFh).
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fn read_unused(&self, addr: Addr) -> u8 {
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let x = (addr / 2) & 0xffff;
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if addr & 1 != 0 {
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(x >> 8) as u8
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} else {
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x as u8
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}
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}
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}
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use super::sysbus::consts::*;
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@ -106,7 +120,7 @@ impl Bus for Cartridge {
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},
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_ => {
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if offset >= self.size {
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0xDD // TODO - open bus implementation
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self.read_unused(addr)
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} else {
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unsafe { *self.bytes.get_unchecked(offset as usize) }
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}
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@ -167,6 +181,10 @@ impl Bus for Cartridge {
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impl DebugRead for Cartridge {
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fn debug_read_8(&mut self, addr: Addr) -> u8 {
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let offset = (addr & 0x01ff_ffff) as usize;
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self.bytes[offset]
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if offset >= self.size {
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self.read_unused(addr)
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} else {
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self.bytes[offset]
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}
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}
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}
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