Merge pull request #11 from danluu/deobfuscate

Various devices

CMOS.js

@@ -27,7 +27,10 @@ function CMOS(PC) {
 }
 CMOS.prototype.ioport_write = function(mem8_loc, data) {
     if (mem8_loc == 0x70) {
-        this.cmos_index = data & 0x7f;
+	// the high order bit is used to indicate NMI masking
+        // low order bits are used to address CMOS
+        // the index written here is used on an ioread 0x71
+        this.cmos_index = data & 0x7f; 
     }
 };
 CMOS.prototype.ioport_read = function(mem8_loc) {
@@ -35,10 +38,13 @@ CMOS.prototype.ioport_read = function(mem8_loc) {
     if (mem8_loc == 0x70) {
         return 0xff;
     } else {
+	// else here => 0x71, i.e., CMOS read
         data = this.cmos_data[this.cmos_index];
         if (this.cmos_index == 10)
+	    // flip the UIP (update in progress) bit on a read
             this.cmos_data[10] ^= 0x80;
         else if (this.cmos_index == 12)
+	    // Always return interrupt status == 0
             this.cmos_data[12] = 0x00;
         return data;
     }

KBD.js

@@ -13,7 +13,7 @@ KBD.prototype.read_status = function(mem8_loc) {
 };
 KBD.prototype.write_command = function(mem8_loc, x) {
     switch (x) {
-        case 0xfe:
+        case 0xfe: // Resend command. Other commands are, apparently, ignored.
             this.reset_request();
             break;
         default:

PCEmulator.js

@@ -185,7 +185,7 @@ PCEmulator.prototype.register_ioport_write = function(start, len, iotype, io_cal
     }
 };
 
-PCEmulator.prototype.ioport80_write = function(mem8_loc, data) {};
+PCEmulator.prototype.ioport80_write = function(mem8_loc, data) {}; //POST codes! Seem to be ignored?
 PCEmulator.prototype.reset = function() { this.request_request = 1; };
 
 

PIC.js

@@ -72,6 +72,16 @@ PIC.prototype.ioport_write = function(mem8_loc, x) {
     mem8_loc &= 1;
     if (mem8_loc == 0) {
         if (x & 0x10) {
+	    /*
+	      ICW1
+	      // 7:5 = address (if MCS-80/85 mode)
+	      // 4 == 1
+	      // 3: 1 == level triggered, 0 == edge triggered
+	      // 2: 1 == call interval 4, 0 == call interval 8
+	      // 1: 1 == single PIC, 0 == cascaded PICs
+	      // 0: 1 == send ICW4
+
+	     */
             this.reset();
             this.init_state = 1;
             this.init4 = x & 1;

PIT.js

@@ -15,6 +15,9 @@ function PIT(PC, ah, bh) {
     }
     this.speaker_data_on = 0;
     this.set_irq = ah;
+    // Ports:
+    // 0x40: Channel 0 data port
+    // 0x61: Control
     PC.register_ioport_write(0x40, 4, 1, this.ioport_write.bind(this));
     PC.register_ioport_read(0x40, 3, 1, this.ioport_read.bind(this));
     PC.register_ioport_read(0x61, 1, 1, this.speaker_ioport_read.bind(this));
@@ -58,22 +61,28 @@ IRQCH.prototype.pit_get_out = function() {
     d = this.get_time() - this.count_load_time;
     switch (this.mode) {
         default:
+	// Interrupt on terminal count
         case 0:
             eh = (d >= this.count) >> 0;
             break;
+	// One shot
         case 1:
             eh = (d < this.count) >> 0;
             break;
+	// Frequency divider
         case 2:
             if ((d % this.count) == 0 && d != 0)
                 eh = 1;
             else
                 eh = 0;
             break;
+	// Square wave
         case 3:
             eh = ((d % this.count) < (this.count >> 1)) >> 0;
             break;
+	// SW strobe
         case 4:
+	// HW strobe
         case 5:
             eh = (d == this.count) >> 0;
             break;