decoupled timers from interpreter tick rate

Interpreter.cpp

@@ -44,13 +44,14 @@ constexpr uint8_t gcvLowResFontData[80] = {
   0xF0, 0x80, 0xF0, 0x80, 0x80
 };
 
-Interpreter::Interpreter(unsigned ticksPerSecond, Display &display, Buzzer &buzzer, Keypad &keypad):
+Interpreter::Interpreter(Display &display, Buzzer &buzzer, Keypad &keypad, CountdownTimer &delayTimer, CountdownTimer &soundTimer):
   mvMemory(scMemorySize),
   mCallStack{},
   mrDisplay{display},
   mrBuzzer{buzzer},
   mrKeypad{keypad},
-  mcTicksPerSecond{ticksPerSecond},
+  mrDelayTimer(delayTimer),
+  mrSoundTimer(soundTimer),
   mvSpecialReg{},
   mvReg{},
   mIsHighResMode{false} {
@@ -143,16 +144,16 @@ void Interpreter::tick() {
   case 0xF000: // several unique instructions
     switch(inst & 0xF0FF) {
     case 0xF007: // FX07 - read timer register
-      mvReg[iRegDst] = (mvSpecialReg[SR_T1] * scTimerFreq + (mcTicksPerSecond - 1)) / mcTicksPerSecond;
+      mvReg[iRegDst] = mrDelayTimer.get();
       break;
     case 0xF015: // FX15 - set timer register
-      mvSpecialReg[SR_T1] = (mcTicksPerSecond * mvReg[iRegDst]) / scTimerFreq;
+      mrDelayTimer.set(mvReg[iRegDst]);
       break;
     case 0xF018: // FX18 - set sound timer register
-      if(mvSpecialReg[SR_T2] == 0 && mvReg[iRegDst] != 0) {
+      if(mvReg[iRegDst] != 0) {
         mrBuzzer.on();
       }
-      mvSpecialReg[SR_T2] = (mcTicksPerSecond * mvReg[iRegDst]) / scTimerFreq;
+      mrSoundTimer.set(mvReg[iRegDst]);
       break;
     case 0xF01E: // FX1E - add to I
       mvSpecialReg[SR_I] += mvReg[iRegDst];
@@ -182,15 +183,8 @@ void Interpreter::tick() {
     break;
   }
 
-  // decrement timers
-  if(mvSpecialReg[SR_T1] > 0) {
-    mvSpecialReg[SR_T1] -= 1;
-  }
-  if(mvSpecialReg[SR_T2] > 0) {
-    mvSpecialReg[SR_T2] -= 1;
-    if(mvSpecialReg[SR_T2] == 0) {
-      mrBuzzer.off();
-    }
+  if(mrSoundTimer.get() == 0) {
+    mrBuzzer.off();
   }
 }