CIA Timers A/B coded.

src/MOSCIA.js

@@ -46,10 +46,55 @@ function TODLatch(cia){
 }
 
 
+function TimerATick(cia){
+  if (cia.__timerA > 0){
+    cia.__timerA -= 1;
+  } else {
+    // Check if Timer A is continuous
+    if (BITM.isOn(cia.__CTA, 3) === 0){
+      cia.__timerA = cia.__timerALatch;
+    } else {
+      // Not continuous, so clear bit 0 (stop timer).
+      cia.__CTA = BITM.clear(cia.__CTA, 0);
+    }
+
+    // Check to see if timer modifies the PORT B bit 6.
+    // If so, determine if it's a pulse or an toggle.
+    if (BITM.isOn(cia.__CTA, 1))
+      cia.__PDB = (BITM.isOn(cia.__CTA, 2) === 0) ? BITM.set(cia.__PDB, 6) : BITM.toggle(cia.__PDB, 6);
+
+    // If timer B is running, and timer B tracks timer A underflows
+    // tick timer B (or, tick it if CNT is positive)
+    if (BITM.isOn(cia.__CTB, 0)){
+      let cs = (this.__CTB & 0x60) >> 5;
+      if (cs === 2 || (cs === 3 && cia.__CNT === 1))
+        TimerBTick(cia);
+    }
+  }
+}
+
+function TimerBTick(cia){
+  if (cia.__timerB > 0){
+    cia.__timerB -= 1;
+  } else {
+    if (BITM.isOn(cia.__CTB, 3) === 0){
+      cia.__timerB = cia.__timerBLatch;
+    } else {
+      cia.__CTB = BITM.clear(cia.__CTB, 0);
+    }
+
+    if (BITM.isOn(cia.__CTB, 1))
+      cia.__PDB = (BITM.isOn(cia.__CTB, 2) === 0) ? BITM.set(cia.__PDB, 7) : BITM.toggle(cia.__PDB, 7);
+  }
+}
+
+
 class MOSCIA{
   constructor(){
     this.__regsel = 0;
 
+    this.__CNT = 0;
+
     this.__PDA = 0;
     this.__PDB = 0;
     this.__DDA = 0;
@@ -87,31 +132,31 @@ class MOSCIA{
       case 0x03: // Data Direction Reg B
         break;
       case 0x04: // Timer A Low
-        break;
+        val = (this.__timerA & 0x00FF); break;
       case 0x05: // Timer A High
-        break
+        val = ((this.__timerA & 0xFF00) >> 4); break;
       case 0x06: // Timer B Low
-        break;
+        val = (this.__timerB & 0x00FF); break;
       case 0x07: // Timer B High
-        break;
+        val = ((this.__timerB & 0xFF00) >> 4); break;
       case 0x08: // 10th of Sec Reg
         this.__TODLatch = 0;
-        return this.__TOD[0]; break;
+        val = this.__TOD[0]; break;
       case 0x09: // Seconds Reg
-        return (this.__TODLatch > 0) ? this.__LTOD[1] : this.__TOD[1]; break;
+        val = (this.__TODLatch > 0) ? this.__LTOD[1] : this.__TOD[1]; break;
       case 0x0A: // Minutes Reg
-        return (this.__TODLatch > 0) ? this.__LTOD[2] : this.__TOD[2]; break;
+        val = (this.__TODLatch > 0) ? this.__LTOD[2] : this.__TOD[2]; break;
       case 0x0B: // Hours AM/PM Reg
         TODLatch(this);
-        return this.__LTOD[3]; break;
+        val = this.__LTOD[3]; break;
       case 0x0C: // Serial Data
         break;
       case 0x0D: // Interrupt Control
         break;
       case 0x0E: // Control Timer Reg A
-        break;
+        val = this.__CTA; break;
       case 0x0F: // Control Timer Reg B
-        break;
+        val = this.__CTB; break;
     }
     return val;
   }
@@ -127,12 +172,16 @@ class MOSCIA{
       case 0x03: // Data Direction Reg B
         break;
       case 0x04: // Timer A Low
+        this.__timerALatch = (this.__timerALatch & 0xFF00) | (d & 0xFF);
         break;
       case 0x05: // Timer A High
+        this.__timerALatch = (this.__timerALatch & 0x00FF) | ((d & 0xFF) << 4);
         break
       case 0x06: // Timer B Low
+        this.__timerBLatch = (this.__timerBLatch & 0xFF00) | (d & 0xFF);
         break;
       case 0x07: // Timer B High
+        this.__timerBLatch = (this.__timerBLatch & 0x00FF) | ((d & 0xFF) << 4);
         break;
       case 0x08: // 10th of Sec Reg
         TODLatch(this);
@@ -163,14 +212,32 @@ class MOSCIA{
       case 0x0D: // Interrupt Control
         break;
       case 0x0E: // Control Timer Reg A
+        this.__CTA = d & 0xFF;
+        if (BITM.isOn(this.__CTA, 4))
+          this.__timerA = this.__timerALatch;
         break;
       case 0x0F: // Control Timer Reg B
+        this.__CTB = d & 0xFF;
+        if (BITM.isOn(this.__CTB, 4))
+          this.__timerB = this.__timerBLatch;
         break;
     }
   }
 
-  get CNT(){return 0;}
-  set CNT(c){}
+  get CNT(){return this.__CNT;}
+  set CNT(c){
+    this.__CNT = (c >= 1) ? 1 : 0;
+    if (this.__CNT === 1){
+      if (BITM.isOn(this.__CTA, 0) && BITM.isOn(this.__CTA, 5))
+        TimerATick(this);
+
+      if (BITM.isOn(this.__CTB, 0){
+        let cs = (this.__CTB & 0x60) >> 5;
+        if (cs === 1)
+          TimerBTick(this);
+      }
+    }
+  }
 
   get SP(){return 0;}
   set SP(b){}
@@ -180,6 +247,20 @@ class MOSCIA{
     if (b > 0 || this.__TODLatch < 2)
       TODTick(this); 
   }
+
+  get phi2(){return 0;}
+  set phi2(p){
+    if (p >= 1){
+      if (BITM.isOn(this.__CTA, 0) && !BITM.isOn(this.__CTA, 5)){
+        TimerATick(this);
+      }
+      if (BITM.isOn(this.__CTB, 0)){
+        let cs = (this.__CTB & 0x60) >> 5;
+        if (cs === 0)
+          TimerBTick(this);
+      }
+    }
+  }
 }