From ccc649bfc14de5858cf227ada5478bdc08effd4c Mon Sep 17 00:00:00 2001
From: Jorj Bauer <jorj@jorj.org>
Date: Wed, 31 May 2017 18:17:25 -0400
Subject: [PATCH] working on mockingboard interrupts

---
 apple/applevm.cpp   |  4 +++-
 apple/sy6522.cpp    | 35 +++++++++++++++++++++++++++++++++--
 apple/sy6522.h      | 13 +++++++++++++
 cpu.cpp             | 10 ++++++++++
 cpu.h               |  4 ++++
 sdl/sdl-speaker.cpp |  7 ++++++-
 6 files changed, 69 insertions(+), 4 deletions(-)

diff --git a/apple/applevm.cpp b/apple/applevm.cpp
index ffdfc6c..85cfa7f 100644
--- a/apple/applevm.cpp
+++ b/apple/applevm.cpp
@@ -23,8 +23,10 @@ AppleVM::AppleVM()
   parallel = new ParallelCard();
   ((AppleMMU *)mmu)->setSlot(1, parallel);
 
+  mockingboard = NULL;
+  /*
   mockingboard = new Mockingboard();
-  ((AppleMMU *)mmu)->setSlot(4, mockingboard);
+  ((AppleMMU *)mmu)->setSlot(4, mockingboard);*/
 
 #ifdef TEENSYDUINO
   teensyClock = new TeensyClock((AppleMMU *)mmu);
diff --git a/apple/sy6522.cpp b/apple/sy6522.cpp
index 059ca25..39f4022 100644
--- a/apple/sy6522.cpp
+++ b/apple/sy6522.cpp
@@ -1,6 +1,8 @@
 #include "sy6522.h"
 #include <stdio.h>
 
+#include "globals.h"
+
 SY6522::SY6522()
 {
   ORB = ORA = 0;
@@ -25,7 +27,7 @@ uint8_t SY6522::read(uint8_t address)
   case SY_DDRA:
     return DDRA;
   case SY_TMR1L:
-      // FIXME: also updates IFR?
+    IFR &= ~SY_IR_TIMER1;
     return (T1_CTR & 0xFF);
   case SY_TMR1H:
     return (T1_CTR >> 8);
@@ -34,7 +36,7 @@ uint8_t SY6522::read(uint8_t address)
   case SY_TMR1HL:
     return (T1_CTR_LATCH >> 8);
   case SY_TMR2L:
-    // FIXME: alos udpates IFR?
+    IFR &= ~SY_IR_TIMER2;
     return (T2_CTR & 0xFF);
   case SY_TMR2H:
     return (T2_CTR >> 8);
@@ -82,6 +84,15 @@ uint8_t SY6522::read(uint8_t address)
     return;
 
   case SY_TMR1H:
+    IFR &= SY_IR_TIMER1;
+
+    // Update IFR?
+    IFR &= 0x7F;
+    if (IFR & IER) {
+      // an interrupt is happening; keep the IE flag on
+      IFR |= 0x80;
+    }
+
     // FIXME: clear interrupt flag
     T1_CTR_LATCH = (T1_CTR_LATCH & 0x00FF) | (val << 8);
     T1_CTR = T1_CTR_LATCH;
@@ -145,6 +156,26 @@ uint8_t SY6522::read(uint8_t address)
 
 void SY6522::update(uint32_t cycles)
 {
+  /* Update 6522 timers */
+
+  // ...
+  /*  
+  SY_IR_CA2       = 1,
+    SY_IR_CA1       = 2,
+    SY_IR_SHIFTREG  = 4,
+    SY_IR_CB2       = 8,
+    SY_IR_CB1       = 16,
+    SY_IR_TIMER2    = 32,
+    SY_IR_TIMER1    = 64,
+    SY_IER_SETCLEAR = 128,
+  SY_IFR_IRQ      = 128
+  */
+  /* Check for 6522 interrupts */
+  if (IFR & 0x80) {
+    g_cpu->stageIRQ();
+  }
+
+  /* Update the attached 8910 chip(s) */
   ay8910[0].update(cycles);
 }
 
diff --git a/apple/sy6522.h b/apple/sy6522.h
index 74b83f8..46107c9 100644
--- a/apple/sy6522.h
+++ b/apple/sy6522.h
@@ -25,6 +25,19 @@ enum {
   SY_ORANOHS = 0x0f  // ORA_NO_HS
 };
 
+// IFR and IER share the names of all but the high bit
+enum {
+  SY_IR_CA2       = 1,
+  SY_IR_CA1       = 2,
+  SY_IR_SHIFTREG  = 4,
+  SY_IR_CB2       = 8,
+  SY_IR_CB1       = 16,
+  SY_IR_TIMER2    = 32,
+  SY_IR_TIMER1    = 64,
+  SY_IER_SETCLEAR = 128,
+  SY_IFR_IRQ      = 128
+};
+
 class SY6522 {
  public:
   SY6522();
diff --git a/cpu.cpp b/cpu.cpp
index f3802c3..b81f9cf 100644
--- a/cpu.cpp
+++ b/cpu.cpp
@@ -407,6 +407,7 @@ void Cpu::Reset()
   x = 0;
   y = 0;
   flags = F_Z | F_UNK; // FIXME: is that F_UNK flag right here?
+  irqPending = false;
 
   if (mmu) {
     pc = readmem(0xFFFC) | (readmem(0xFFFD) << 8);
@@ -495,6 +496,11 @@ uint8_t Cpu::Run(uint8_t numSteps)
 
 uint8_t Cpu::step()
 {
+  if (irqPending) {
+    irqPending = false;
+    irq();
+  }
+
   uint8_t m = readmem(pc++);
 
   optype_t opcode = opcodes[m];
@@ -1050,3 +1056,7 @@ uint16_t Cpu::popS16()
   return (msb << 8) | lsb;
 }
 
+void Cpu::stageIRQ()
+{
+  irqPending = true;
+}
diff --git a/cpu.h b/cpu.h
index 00b87cc..29877fb 100644
--- a/cpu.h
+++ b/cpu.h
@@ -45,6 +45,8 @@ class Cpu {
   uint8_t SP();
   uint8_t P();
 
+  void stageIRQ();
+
  protected:
   // Stack manipulation
   void pushS8(uint8_t b);
@@ -64,6 +66,8 @@ class Cpu {
   uint8_t flags;
 
   uint32_t cycles;
+
+  bool irqPending;
   
   MMU *mmu;
 };
diff --git a/sdl/sdl-speaker.cpp b/sdl/sdl-speaker.cpp
index 54ab85f..2308610 100644
--- a/sdl/sdl-speaker.cpp
+++ b/sdl/sdl-speaker.cpp
@@ -133,14 +133,19 @@ void SDLSpeaker::maintainSpeaker(uint32_t c)
   // The "terribad" audio gets two shares. THis means we've got 8 total 
   // "voices" -- 6 from the mockingboard and 2 from the built-in. 8 is 
   // a great number for dividing. :)
-  mixerValue += (toggleState ? 0xFF : 0x00);
+  mixerValue += (toggleState ? 0x1FF : 0x00);
   numMixed += 2;
 
+#if 0
   if (numMixed != 8) {
     printf("SPEAKER FAIL - should always be 8\n");
   }
 
   mixerValue >>= 3; // divide by 8
+#else
+  mixerValue /= numMixed;
+#endif
+
 
   // FIXME: g_volume