-
Notifications
You must be signed in to change notification settings - Fork 0
/
mapper000.go
61 lines (50 loc) · 1.06 KB
/
mapper000.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
package nes
type Mapper000 struct {
PrgBanks byte
ChrBanks byte
}
func NewMapper000(prgRomChunks, chrRomChunks byte) Mapper000 {
return Mapper000{
PrgBanks: prgRomChunks,
ChrBanks: chrRomChunks,
}
}
// Address Mapping
//
// if 16KB ROM size:
// 0x8000-0xBFFF -> 0x0000-0x3FFF
// 0xC000-0xFFFF -> 0x0000-0x3FFF (mirror)
//
// if 32KB ROM size:
// 0x8000-0xFFFF -> 0x0000-0x7FFF
func (m Mapper000) cpuMapRead(addr uint16) uint16 {
if addr >= 0x8000 && addr <= 0xFFFF {
if m.PrgBanks > 1 {
addr &= 0x7FFF // 32KB ROM
} else {
addr &= 0x3FFF // 16KB ROM, need to mirror
}
}
return addr
}
func (m Mapper000) cpuMapWrite(addr uint16) uint16 {
if addr >= 0x8000 && addr <= 0xFFFF {
if m.PrgBanks > 1 {
addr &= 0x3FFF // 16KB ROM, need to mirror
} else {
addr &= 0x7FFF // 32KB ROM
}
}
return addr
}
// No PPU mapping
func (m Mapper000) ppuMapRead(addr uint16) uint16 {
if addr >= 0x0000 && addr <= 0x1FFF {
}
return addr
}
func (m Mapper000) ppuMapWrite(addr uint16) uint16 {
if addr >= 0x0000 && addr <= 0x1FFF {
}
return addr
}