Decimal mode working, all Klaus tests passing

Author: bencoder

Processor.ts

@@ -152,10 +152,30 @@ export class Processor {
  }
 
  private convertToBCD(value: number): number {
- value = value % 100; //discard any remainder
+ while (value < 0) {
+ value += 100;
+ }
+ value = value % 100; //discard any remainder over 100
  const highNibble = Math.floor(value / 10);
  const lowNibble = value - highNibble * 10;
- return highNibble << (4 + lowNibble);
+ return (highNibble << 4) + lowNibble;
+ }
+
+ //We can't use the adc with ~v2 for subtraction in decimal mode
+ private decimalSub(v1: number, v2: number) {
+ const c = (this.registers[FLAGS] & FLAG_C) > 0 ? 0 : 1; //not-c
+ v1 = this.convertFromBCD(v1);
+ v2 = this.convertFromBCD(v2);
+ const sum = v1 - v2 - c;
+ if (sum < 0) {
+ this.unsetFlag(FLAG_C);
+ } else {
+ this.setFlag(FLAG_C);
+ }
+ const result = this.convertToBCD(sum);
+ //only C is valid in Decimal mode, but try to set the others anyway
+ this.setFlagsFor(result);
+ return result;
  }
 
  private internaladc(v1: number, v2: number) {
@@ -398,9 +418,15 @@ export class Processor {
  private sbc(operand: number, getAddress?: (operand: number) => number) {
  const v1 = this.registers[A];
  const v2 = getAddress ? this.readMem(getAddress(operand)) : operand;
- //sbc should be the same operation as adc but with the bits of the memory byte flipped
- //>>> coerces to an unsigned int so that the bitwise invert ~ works as expected, otherwise in JS ~0xff == -255
- const sum = this.internaladc(v1, (~v2 >>> 0) & 0xff);
+ const decimalMode = (this.registers[FLAGS] & FLAG_D) > 0;
+ let sum;
+ if (decimalMode) {
+ sum = this.decimalSub(v1, v2);
+ } else {
+ //binary sbc should be the same operation as adc but with the bits of the memory byte flipped
+ //>>> coerces to an unsigned int so that the bitwise invert ~ works as expected, otherwise in JS ~0xff == -255
+ sum = this.internaladc(v1, (~v2 >>> 0) & 0xff);
+ }
  this.registers[A] = sum;
  }
 

test/test.ts

@@ -9,7 +9,7 @@ const processor = new Processor(ram);
 processor.setPC(0x0400);
 
 //output debug data when the PC is between these values
-const traceStart = 0x346f;
+const traceStart = 0xffff;
 const traceEnd = 0x3500;
 
 let cycles = 0;