mirror of
https://github.com/Candygoblen123/SwiftNES.git
synced 2024-11-09 22:46:24 -06:00
42 lines
1.6 KiB
Swift
42 lines
1.6 KiB
Swift
// 7 bit 0
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// ---- ----
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// VPHB SINN
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// |||| ||||
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// |||| ||++- Base nametable address
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// |||| || (0 = $2000; 1 = $2400; 2 = $2800; 3 = $2C00)
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// |||| |+--- VRAM address increment per CPU read/write of PPUDATA
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// |||| | (0: add 1, going across; 1: add 32, going down)
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// |||| +---- Sprite pattern table address for 8x8 sprites
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// |||| (0: $0000; 1: $1000; ignored in 8x16 mode)
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// |||+------ Background pattern table address (0: $0000; 1: $1000)
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// ||+------- Sprite size (0: 8x8 pixels; 1: 8x16 pixels)
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// |+-------- PPU master/slave select
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// | (0: read backdrop from EXT pins; 1: output color on EXT pins)
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// +--------- Generate an NMI at the start of the
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// vertical blanking interval (0: off; 1: on)
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struct ControlRegister: OptionSet {
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var rawValue: UInt8
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static let NAMETABLE1 = ControlRegister(rawValue: 0b00000001)
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static let NAMETABLE2 = ControlRegister(rawValue: 0b00000010)
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static let VRAM_ADD_INCREMENT = ControlRegister(rawValue: 0b00000100)
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static let SPRITE_PATTERN_ADDR = ControlRegister(rawValue: 0b00001000)
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static let BACKROUND_PATTERN_ADDR = ControlRegister(rawValue: 0b00010000)
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static let SPRITE_SIZE = ControlRegister(rawValue: 0b00100000)
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static let MASTER_SLAVE_SELECT = ControlRegister(rawValue: 0b01000000)
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static let GENERATE_NMI = ControlRegister(rawValue: 0b10000000)
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func vramAddrIncrement() -> UInt8 {
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if self.contains(.VRAM_ADD_INCREMENT) {
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1
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} else {
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32
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}
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}
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func generateVblankNMI() -> Bool {
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self.contains(.GENERATE_NMI)
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}
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}
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