MOSCIA More Timer A Tests.

test/unit.src.MOSCIA.spec.js

     expect(IC & 0x80).to.be.equal(0x80);
   });
 
-  it("Timer A", function(){
+  it("Timer A, phi2 Triggered, Interrupt Verification", function(){
     let cia = new MOSCIA();
     let tick = (cycles) => {
       for (let i=0; i < cycles; i++)
     expect(IC & 0x01).to.be.equal(0x01);
     expect(IC & 0x80).to.be.equal(0x80);
   });
+
+
+  it("Timer A, CNT Triggered, Underflow report to Port B", function(){
+    let cia = new MOSCIA();
+    let tick = (cycles, cnt) => {
+      cnt = (cnt === true);
+      for (let i=0; i < cycles; i++){
+        if (cnt)
+          cia.CNT = 1;
+        cia.phi2 = 1;
+        if (cnt)
+          cia.CNT = 0;
+      }
+    };
+
+    cia.RS = 0x04;
+    cia.DATA = 0x08;
+    cia.RS = 0x05;
+    cia.DATA = 0x00;
+
+    cia.RS = 0x0E;
+    // Force latch load into Timer A,
+    // enable underflow reporting on Port B bit 6,
+    // set Timer A to trigger on CNT,
+    // and activate Timer A
+    cia.DATA = 0x33;
+
+    cia.RS = 0x04;
+    // First, test a few ticks where CNT is not high.
+    expect(cia.DATA).to.be.equal(0x08); // Validate inital timer value.
+    tick(1);
+    tick(1);
+    tick(1);
+    tick(1);
+    expect(cia.DATA).to.be.equal(0x08);
+
+    // Now verify CNT triggers!
+    tick(1, true);
+    expect(cia.DATA).to.be.equal(0x07);
+    tick(1, true);
+    expect(cia.DATA).to.be.equal(0x06);
+    tick(1, true);
+    tick(1, true);
+    tick(1, true);
+    tick(1, true);
+    tick(1, true);
+    tick(1, true);
+    expect(cia.DATA).to.be.equal(0x00);
+    tick(1, true);
+
+    // Double check that timer has reset to latch value...
+    expect(cia.DATA).to.be.equal(0x08);
+
+    // Verify Interrupt (again... but it doesn't hurt!)
+    cia.RS = 0x0D;
+    let IC = cia.DATA;
+    expect(IC & 0x01).to.be.equal(0x01);
+    expect(IC & 0x80).to.be.equal(0x80);
+
+    // Checking Port B bit 6 which should only go high for 1 cycle!
+    cia.RS = 0x01;
+    expect(cia.DATA & 0x40).to.be.equal(0x40);
+    tick(1, true);
+    expect(cia.DATA & 0x40).to.be.equal(0x00);
+
+    // Check Port B bit 6 toggling...
+    // -------------------------------------------
+    // Force latch load into Timer A,
+    // enable underflow reporting on Port B bit 6,
+    // setup Port B bit 6 to invert,
+    // set Timer A to trigger on CNT,
+    // and activate Timer A
+    cia.RS = 0x0E;
+    cia.DATA = 0x37;
+
+    for (let i=0; i < 9; i++)
+      tick(1, true);
+    cia.RS = 0x04;
+    expect(cia.DATA).to.be.equal(0x08);
+
+    cia.RS = 0x01;
+    expect(cia.DATA & 0x40).to.be.equal(0x40);
+    tick(1, true);
+    expect(cia.DATA & 0x40).to.be.equal(0x40);
+    cia.RS = 0x04;
+    expect(cia.DATA).to.be.equal(0x07);
+
+    for (let i=0; i < 8; i++)
+      tick(1, true);
+    expect(cia.DATA).to.be.equal(0x08);
+    cia.RS = 0x01;
+    expect(cia.DATA & 0x40).to.be.equal(0x00);
+  });
 });