70 lines
1.3 KiB
Zig
70 lines
1.3 KiB
Zig
const types = @import("types.zig");
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const Mirroring = types.Mirroring;
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const Mapper13 = @This();
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chr_bank: u8 = 0,
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fixed_mirroring: Mirroring,
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prg_mask: usize,
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pub fn init(
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prg_size: usize,
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mirroring_mode: Mirroring,
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) Mapper13 {
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return .{
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.fixed_mirroring = mirroring_mode,
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.prg_mask = if (prg_size > 0) prg_size - 1 else 0x7fff,
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};
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}
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pub fn cpuMapRead(
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self: *const Mapper13,
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address: u16,
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) ?usize {
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if (address < 0x8000) return null;
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return (@as(usize, address) - 0x8000) & self.prg_mask;
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}
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pub fn cpuWrite(
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self: *Mapper13,
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address: u16,
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value: u8,
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) void {
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if (address < 0x8000) return;
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self.chr_bank = value & 0x03;
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}
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pub fn ppuMapRead(
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self: *const Mapper13,
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address: u16,
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) ?usize {
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if (address >= 0x2000) return null;
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if (address < 0x1000) {
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return 0x80000000 | @as(usize, address);
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} else {
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const bank = @as(usize, self.chr_bank & 3);
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const offset = @as(usize, address & 0x0fff);
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return 0x80000000 | (bank * 0x1000 + offset);
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}
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}
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pub fn ppuMapWrite(
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self: *const Mapper13,
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address: u16,
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) ?usize {
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return self.ppuMapRead(address);
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}
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pub fn mirroring(
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self: *const Mapper13,
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) Mirroring {
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return self.fixed_mirroring;
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}
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pub fn irqAsserted(
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_: *const Mapper13,
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) bool {
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return false;
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}
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