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feat(bus): implement Gameboy Advance MMIO

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This commit is contained in:
Rekai Nyangadzayi Musuka
2022-10-21 05:11:45 -03:00
parent 5cbfae677a
commit d50aff30c9
5 changed files with 132 additions and 53 deletions
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10
src/cpu/half_signed_data_transfer.zig
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@@ -34,17 +34,17 @@ pub fn comptimeHalfSignedDataTransfer(comptime P: bool, comptime U: bool, compti
},
0b01 => {
// LDRH
const halfword = bus.readHalfWord(address);
const halfword = bus.read16(address);
cpu.r[rd] = @as(u32, halfword);
},
0b10 => {
// LDRSB
const byte = bus.readByte(address);
const byte = bus.read8(address);
cpu.r[rd] = util.u32SignExtend(8, @as(u32, byte));
},
0b11 => {
// LDRSH
const halfword = bus.readHalfWord(address);
const halfword = bus.read16(address);
cpu.r[rd] = util.u32SignExtend(16, @as(u32, halfword));
},
}
@@ -53,8 +53,8 @@ pub fn comptimeHalfSignedDataTransfer(comptime P: bool, comptime U: bool, compti
// STRH
const src = @truncate(u16, cpu.r[rd]);
bus.writeHalfWord(address + 2, src);
bus.writeHalfWord(address, src);
bus.write16(address + 2, src);
bus.write16(address, src);
} else {
std.debug.panic("TODO Figure out if this is also SWP", .{});
}

14
src/cpu/single_data_transfer.zig
View File

@@ -21,29 +21,29 @@ pub fn comptimeSingleDataTransfer(comptime I: bool, comptime P: bool, comptime U
if (L) {
if (B) {
// LDRB
cpu.r[rd] = bus.readByte(address);
cpu.r[rd] = bus.read8(address);
} else {
// LDR
// FIXME: Unsure about how I calculate the boundary offset
cpu.r[rd] = std.math.rotl(u32, bus.readWord(address), address % 4);
cpu.r[rd] = std.math.rotl(u32, bus.read32(address), address % 4);
}
} else {
if (B) {
// STRB
const src = @truncate(u8, cpu.r[rd]);
bus.writeByte(address + 3, src);
bus.writeByte(address + 2, src);
bus.writeByte(address + 1, src);
bus.writeByte(address, src);
bus.write8(address + 3, src);
bus.write8(address + 2, src);
bus.write8(address + 1, src);
bus.write8(address, src);
} else {
// STR
// FIXME: Is this right?
const src = cpu.r[rd];
const aligned_addr = address - (address % 4);
bus.writeWord(aligned_addr, src);
bus.write32(aligned_addr, src);
}
}