irq+nmi buttons in debug window

src/main/kotlin/razorvine/examplemachine/GUI.kt

@@ -204,8 +204,10 @@ class DebugWindow(val vm: VirtualMachine) : JFrame("debugger"), ActionListener {
 
         val resetBt = JButton("Reset").also { it.actionCommand = "reset" }
         val cycleBt = JButton("Step").also { it.actionCommand = "step" }
+        val irqBt = JButton("IRQ").also { it.actionCommand = "irq" }
+        val nmiBt = JButton("NMI").also { it.actionCommand = "nmi" }
         val quitBt = JButton("Quit").also { it.actionCommand = "quit" }
-        listOf(resetBt, cycleBt, pauseBt, quitBt).forEach {
+        listOf(resetBt, cycleBt, irqBt, nmiBt, pauseBt, quitBt).forEach {
             it.addActionListener(this)
             buttonPanel.add(it)
         }
@@ -235,6 +237,8 @@ class DebugWindow(val vm: VirtualMachine) : JFrame("debugger"), ActionListener {
                 pauseBt.actionCommand = "pause"
                 pauseBt.text = "Pause"
             }
+            "irq" -> vm.cpu.irq()
+            "nmi" -> vm.cpu.nmi()
             "quit" -> {
                 dispatchEvent(WindowEvent(this, WindowEvent.WINDOW_CLOSING))
             }

src/main/kotlin/razorvine/ksim65/Cpu6502.kt

@@ -107,7 +107,11 @@ open class Cpu6502(private val stopOnBrk: Boolean = false) : BusComponent() {
         get() = currentInstruction.mnemonic
 
     // has an interrupt been requested?
-    protected var pendingInterrupt: Pair<Boolean, BusComponent>? = null
+    protected enum class Interrupt {
+        IRQ,
+        NMI
+    }
+    protected var pendingInterrupt: Interrupt? = null
 
     // data byte from the instruction (only set when addr.mode is Accumulator, Immediate or Implied)
     protected var fetchedData: Int = 0
@@ -334,13 +338,13 @@ open class Cpu6502(private val stopOnBrk: Boolean = false) : BusComponent() {
         while (instrCycles > 0) clock()
     }
 
-    fun nmi(source: BusComponent) {
-        pendingInterrupt = Pair(true, source)
+    fun nmi() {
+        pendingInterrupt = Interrupt.NMI
     }
 
-    fun irq(source: BusComponent) {
+    fun irq() {
         if (!regP.I)
-            pendingInterrupt = Pair(false, source)
+            pendingInterrupt = Interrupt.IRQ
     }
 
     fun logState(): String =
@@ -1092,19 +1096,17 @@ open class Cpu6502(private val stopOnBrk: Boolean = false) : BusComponent() {
 
     protected open fun iBrk() {
         // handle BRK ('software interrupt') or a real hardware IRQ
-        val interrupt = pendingInterrupt
-        val nmi = interrupt?.first == true
-        if (interrupt != null) {
+        if (pendingInterrupt != null) {
             pushStackAddr(regPC - 1)
         } else {
             regPC++
             pushStackAddr(regPC)
         }
-        regP.B = interrupt == null
+        regP.B = pendingInterrupt == null
         pushStack(regP)
         regP.I = true     // interrupts are now disabled
         // NMOS 6502 doesn't clear the D flag (CMOS 65C02 version does...)
-        regPC = readWord(if (nmi) NMI_vector else IRQ_vector)
+        regPC = readWord(if (pendingInterrupt==Interrupt.NMI) NMI_vector else IRQ_vector)
         pendingInterrupt = null
     }
 

src/main/kotlin/razorvine/ksim65/Cpu65C02.kt

@@ -637,15 +637,14 @@ class Cpu65C02(stopOnBrk: Boolean = false) : Cpu6502(stopOnBrk) {
 
     override fun iBrk() {
         // handle BRK ('software interrupt') or a real hardware IRQ
-        val interrupt = pendingInterrupt
-        val nmi = interrupt?.first == true
-        if (interrupt != null) {
+        val nmi = pendingInterrupt == Interrupt.NMI
+        if (pendingInterrupt != null) {
             pushStackAddr(regPC - 1)
         } else {
             regPC++
             pushStackAddr(regPC)
         }
-        regP.B = interrupt == null
+        regP.B = pendingInterrupt == null
         pushStack(regP)
         regP.I = true     // interrupts are now disabled
         regP.D = false    // this is different from NMOS 6502

src/main/kotlin/razorvine/ksim65/components/Timer.kt

@@ -34,9 +34,9 @@ class Timer(startAddress: Address, endAddress: Address, val cpu: Cpu6502) : MemM
             counter++
             if (counter == interval) {
                 if (nmi)
-                    cpu.nmi(this)
+                    cpu.nmi()
                 else
-                    cpu.irq(this)
+                    cpu.irq()
                 counter = 0
             }
         }

src/main/resources/vmdemo.asm

@@ -6,6 +6,7 @@
 	TIMER	= $d200
 	MOUSE   = $d300
 	KEYBOARD = $d400
+	IRQVEC  = $fffe
 	SCREEN_WIDTH=640
 
 	* = $1000
@@ -13,8 +14,21 @@
 start
 	sei
 	ldx  #$ff
-	txs
-	cli
+	txs		; clear the stack
+	; setup timer irq
+	lda  #<irq
+	sta  IRQVEC
+	lda  #>irq
+	sta  IRQVEC+1
+	lda  #<1000
+	sta  TIMER+1	; every 1000 clock cycles an irq
+	lda  #>1000
+	sta  TIMER+2
+	lda  #0
+	sta  TIMER+3
+	lda  #1
+	sta  TIMER+0
+	cli		; enable irqs
 
 ; ------- print stuff
 	lda  #10
@@ -127,3 +141,50 @@ done	jmp  done
 
 
 character .byte 0
+
+; ---------- irq routine
+;   this one simply read the RTC and prints it on the bottom of the screen.
+irq
+	pha
+	txa
+	pha
+	tya
+	pha
+	; we don't check for BRK flag because we're lazy
+	lda  DISPLAY+0
+	pha
+	lda  DISPLAY+1
+	pha
+	ldy  #29
+	sty  DISPLAY+1
+	ldy  #0
+	sty  DISPLAY+0
+-	lda  _time_msg,y
+	beq  +
+	sta  DISPLAY+2
+	inc  DISPLAY+0
+	iny
+	bne  -
++	; read the clock now
+	ldx  #0
+-	lda  RTC,x
+	clc
+	adc  #32
+	sta  DISPLAY+2
+	inc  DISPLAY+0
+	inx
+	cpx  #9
+	bne  -
+
+	pla
+	sta  DISPLAY+1
+	pla
+	sta  DISPLAY+0
+	pla
+	tay
+	pla
+	tax
+	pla
+	rti
+
+_time_msg	.text  "The time is: ",0