PPU: background rendering

Sources/CPU/CPU.swift

@@ -157,9 +157,10 @@ class CPU {
     func run(onCycle: @escaping () -> (), onComplete: @escaping () -> ())  {
         let opcodes = OPCODES_MAP
         while true {
-            if let _nmi = bus.pollNMI() {
-                
+            if bus.pollNMI() != nil {
+                print(programCounter)
                 interrupt(.NMI)
+                print(programCounter)
             }
             processOpcodes(onCycle: onCycle, opcodes: opcodes) {
                 onComplete()

Sources/CPU/Trace.swift

@@ -9,7 +9,7 @@ func dumpCpuState(_ cpu: CPU) -> String {
         {
             let (addr, _) = cpu.getAbsoluteAddress(opcode.mode, addr: cpu.programCounter + 1)
 
-            return (addr, cpu.memRead(addr))
+            return (addr, 0)//cpu.memRead(addr))
         }()
     }
 

Sources/Data/Bus.swift

@@ -32,7 +32,7 @@ class Bus {
     }
 
     func pollNMI() -> UInt8? {
-        ppu.nmiInterrupt
+        ppu.pollNMI()
     }
 }
 

Sources/PPU/NesPPU.swift

@@ -18,7 +18,7 @@ class NesPPU {
     var scanline: UInt16 = 0
     var cycles: Int = 0
 
-    var nmiInterrupt: UInt8?
+    var nmiInterrupt: UInt8? = nil
 
     init(_ chrRom: [UInt8], _ mirroring: Mirroring) {
         self.chrRom = chrRom
@@ -52,6 +52,12 @@ class NesPPU {
         return false
     }
 
+    func pollNMI() -> UInt8? {
+        let tmp = self.nmiInterrupt
+        self.nmiInterrupt = nil
+        return tmp
+    }
+
     func writeToPPUAddr(_ value: UInt8) {
         addr.update(value)
     }
@@ -110,7 +116,7 @@ class NesPPU {
 
     func writeToData(_ data: UInt8) {
         let addr = addr.get()
-        //print("\(addr): \(data)")
+        print("\(addr): \(data)")
         switch addr {
         case 0...0x1fff:
             print("Attempt to write to chr rom space \(addr)!")

Sources/PPU/Registers/ControlRegister.swift

@@ -28,7 +28,7 @@ struct ControlRegister: OptionSet {
     static let GENERATE_NMI = ControlRegister(rawValue: 0b10000000)
 
     func vramAddrIncrement() -> UInt8 {
-        if self.contains(.VRAM_ADD_INCREMENT) {
+        if !self.contains(.VRAM_ADD_INCREMENT) {
             1
         } else {
             32
@@ -40,7 +40,7 @@ struct ControlRegister: OptionSet {
     }
 
     func backgroundPatternAddr() -> Int {
-        if self.contains(.BACKROUND_PATTERN_ADDR) {
+        if !self.contains(.BACKROUND_PATTERN_ADDR) {
             0
         } else {
             0x1000