RealQ16s:Provisional register listing

These are the minimum required registers for the RealQ16s project - that is there may be more registers than this in an actual machine (depending on extensions) but these /must/ be present.

Core registers

Core registers
RealQ16s
General purpose
A (16bit)	Accumulator, ALU operand
B (16bit)	Base register, pointers
C (16bit)	Count register, offsets
D (16bit)	Data, communications
Note:	Each GP register has a L and H form, eg AL is the lower 8 bits of A
Programming registers
IP (16bit)	Instruction pointer
SP (16bit)	Stack pointer
BP (16bit)	Stack frame pointer
STRIDE (4bit)	For array access

These registers are required by all implementations of RealQ16s

• General purpose - There are 8 bytes of general purpose registers.
  • There are 4 16 bit general purpose registers, A, B, C and D. Each of these is aliased to 2 8 bit registers, they are:
    • AL, AH, BL, BH, CL, CH, DL and DH. That is AL is the lower byte of A and AH the upper, same for the others.
  • To sum up the registers are as follows:

  [ilmath]\overbrace{\ \ \overbrace{\text{8 bits} }^\text{AL}\ \ \ \vert\ \ \ \overbrace{\text{8 bits} }^\text{AH}\ \ }^\text{A}[/ilmath] [ilmath]\Big\vert[/ilmath] [ilmath]\overbrace{\ \ \overbrace{\text{8 bits} }^\text{BL}\ \ \ \vert\ \ \ \overbrace{\text{8 bits} }^\text{BH}\ \ }^\text{B}[/ilmath] [ilmath]\Big\vert[/ilmath] [ilmath]\overbrace{\ \ \overbrace{\text{8 bits} }^\text{CL}\ \ \ \vert\ \ \ \overbrace{\text{8 bits} }^\text{CH}\ \ }^\text{C}[/ilmath] [ilmath]\Big\vert[/ilmath] [ilmath]\overbrace{\ \ \overbrace{\text{8 bits} }^\text{DL}\ \ \ \vert\ \ \ \overbrace{\text{8 bits} }^\text{DH}\ \ }^\text{D}[/ilmath]

• Instruction pointer

  [ilmath]\overbrace{\ \ \text{8 bits}\ \ \ \vert\ \ \ \text{8 bits}\ \ }^\text{IP}[/ilmath]

• Stack registers
  • There are 2 stack registers, BP, which points to the base of the current stack frame and SP, which points to the head of the stack.

  [ilmath]\overbrace{\ \ \text{8 bits}\ \ \ \vert\ \ \ \text{8 bits}\ \ }^\text{BP}[/ilmath] [ilmath]\Big\vert[/ilmath] [ilmath]\overbrace{\ \ \text{8 bits}\ \ \ \vert\ \ \ \text{8 bits}\ \ }^\text{SP}[/ilmath]

• Stride register

  [ilmath]\overbrace{\ \ \text{4 bits}\ \ \ }^\text{STRIDE}[/ilmath]