SwiftNES/Sources/PPU/Registers/AddrRegister.swift
2024-08-19 11:21:24 -04:00

43 lines
887 B
Swift

class AddrRegister {
private var value: (UInt8, UInt8) = (0, 0) // hi byte first, lo byte second
private var hiPointer = true
func set(_ data: UInt16) {
value.0 = UInt8(data >> 8)
value.1 = UInt8(data & 0xff)
}
func update(_ data: UInt8) {
if hiPointer {
value.0 = data
} else {
value.1 = data
}
if get() > 0x3fff {
set(get() & 0b11111111111111)
}
hiPointer.toggle()
}
func increment(_ inc: UInt8) {
let lo = value.1
value.1 = value.1 &+ inc
if lo > value.1 {
value.0 = value.0 &+ 1
}
if get() > 0x3fff {
set(get() & 0b11111111111111)
}
}
func resetLatch() {
hiPointer = true
}
func get() -> UInt16 {
UInt16(value.0) << 8 | UInt16(value.1)
}
}