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feat: impelemt THUMB open bus

This commit is contained in:
Rekai Nyangadzayi Musuka 2022-04-14 00:21:49 -03:00
parent 9b9b6c0d6f
commit f6d746e810
1 changed files with 26 additions and 7 deletions
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33
src/Bus.zig
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@ -84,12 +84,31 @@ pub fn debugRead(self: *const Self, comptime T: type, address: u32) T {
}
fn readOpenBus(self: *const Self, comptime T: type, address: u32) T {
if (self.cpu.?.cpsr.t.read()) {
log.err("TODO: {} open bus read in THUMB", .{T});
return 0;
}
const r15 = self.cpu.?.r[15];
const word = if (self.cpu.?.cpsr.t.read()) blk: {
const page = @truncate(u8, r15 >> 24);
switch (page) {
// EWRAM, PALRAM, VRAM, and Game ROM (16-bit)
0x02, 0x05, 0x06, 0x08...0x0D => {
const halfword = self.debugRead(u16, r15 + 2);
break :blk @as(u32, halfword) << 16 | halfword;
},
// BIOS or OAM (32-bit)
0x00, 0x07 => {
const offset: u32 = if (address & 3 == 0b00) 2 else 0;
break :blk @as(u32, self.debugRead(u16, (r15 + 2) + offset)) << 16 | self.debugRead(u16, r15 + offset);
},
// IWRAM (16-bit but special)
0x03 => {
const offset: u32 = if (address & 3 == 0b00) 2 else 0;
break :blk @as(u32, self.debugRead(u16, (r15 + 2) - offset)) << 16 | self.debugRead(u16, r15 + offset);
},
else => unreachable,
}
} else self.debugRead(u32, r15 + 4);
const word = self.debugRead(u32, self.cpu.?.r[15] + 4);
return @truncate(T, rotr(u32, word, 8 * (address & 3)));
}
@ -152,7 +171,7 @@ pub fn write(self: *Self, comptime T: type, address: u32, value: T) void {
0x07 => self.ppu.oam.write(T, align_addr, value),
// External Memory (Game Pak)
0x08...0x0D => {},
0x08...0x0D => {}, // EEPROM
0x0E...0x0F => {
const rotate_by = switch (T) {
u32 => address & 3,
@ -163,7 +182,7 @@ pub fn write(self: *Self, comptime T: type, address: u32, value: T) void {
self.pak.backup.write(address, @truncate(u8, rotr(T, value, 8 * rotate_by)));
},
else => undWrite("Tried to write {} 0x{X:} to 0x{X:0>8}", .{ T, value, address }),
else => {},
}
}