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loopregister.go
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loopregister.go
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package register
type VRAMRegister struct {
Unused uint16 // 1000 0000 0000 0000 // 1
FineY uint16 // 0111 0000 0000 0000 // 3
NameTableY uint16 // 0000 1000 0000 0000 // 1
NameTableX uint16 // 0000 0100 0000 0000 // 1
CoarseY uint16 // 0000 0011 1110 0000 // 5
CoarseX uint16 // 0000 0000 0001 1111 // 5
}
func (r *VRAMRegister) Value() uint16 {
res := uint16(0x0)
res |= (r.Unused << 15)
res |= (r.FineY << 12)
res |= (r.NameTableY << 11)
res |= (r.NameTableX << 10)
res |= (r.CoarseY << 5)
res |= (r.CoarseX)
return res
}
func (r *VRAMRegister) Set(val uint16) {
r.Unused = bit16(val, 15)
r.FineY = (val & (0x7000)) >> 12
r.NameTableY = bit16(val, 11)
r.NameTableX = bit16(val, 10)
r.CoarseY = (val & (0x03E0)) >> 5
r.CoarseX = val & 0x001F
}
func (r *VRAMRegister) Increment(val int) {
r.Set(r.Value() + uint16(val))
}
func (r *VRAMRegister) And(val uint16) {
r.Set(r.Value() & val)
}
func (r *VRAMRegister) FlipNameTableX() {
if r.NameTableX == 0 {
r.NameTableX = 1
} else {
r.NameTableX = 0
}
}
func (r *VRAMRegister) FlipNameTableY() {
if r.NameTableY == 0 {
r.NameTableY = 1
} else {
r.NameTableY = 0
}
}
func (r *VRAMRegister) Copy(src *VRAMRegister) {
r.Unused = src.Unused
r.FineY = src.FineY
r.NameTableY = src.NameTableY
r.NameTableX = src.NameTableX
r.CoarseY = src.CoarseY
r.CoarseX = src.CoarseX
}
func bit16(n uint16, pos uint8) uint16 {
val := n & (1 << pos)
if val > 0 {
return 1
}
return 0
}