private int POP(RegisterIndexPair rp)
{
/*
* Stack:
* E rp+1
* D rp
*/
registers[rp.RHS] = Pop8();
registers[rp.LHS] = Pop8();
if (rp == RegisterIndexPair.PSW)
{
/*http://www.vcfed.org/forum/archive/index.php/t-63090.html
* Issue #1: Always Clear Bit 5 and Bit 3, and Set Bit 1 for POP PSW
* instruction.
*/
/*Flags &= (0xff - 0x20 - 0x08);
* Flags |= 2;*/
Flags &= 0b11010111;
Flags |= 0b00000010;
}
return(10);
}
// The most significant 8 bits of data are stored at the memory address one less than the contents of the stack pointer.
// The least significant 8 bits of data are stored at the memory address two less than the contents of the stack pointer.
private int PUSH(RegisterIndexPair rp)
{
/*
* Assume that register D contains 8F,
* register E contains 9D,
* and the stack pointer contains 3A2C.
*
* 3A2C ?? <-- stackPointer
*
* Then the instruction: PUSH D
*
* stores the D register at memory address 3A2B, stores the E register at memory address 3A2A, and then
* decrements the stack pointer by two, leaving the stack pointer equal to 3A2A.
*
* 3A2A 9D (contents of E) <-- stackPointer
* 3A2B 8F (contents of D)
* 3A2C ??
*/
Push8(registers[rp.LHS]);
Push8(registers[rp.RHS]);
return(11);
}
// "If register B contains 3F and register C contains 16,
// the instruction: STAX B will store the contents of the accumulator at memory location 3F16H."
private int STAX(RegisterIndexPair rp)
{
mem[registers[rp]] = Accumulator;
return(7);
}
// LDAX Load Accumulator
// If register D contains 93H and register E contains 8BH, the instruction: LDAX D will load the accumulator from memory location 938BH.
private int LDAX(RegisterIndexPair rp)
{
Accumulator = mem[registers[rp]];
return(7);
}