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:

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

• Instruction pointer

  $\overbrace{\ \ \text{8 bits}\ \ \ \vert\ \ \ \text{8 bits}\ \ }^\text{IP}$

• 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.

  $\overbrace{\ \ \text{8 bits}\ \ \ \vert\ \ \ \text{8 bits}\ \ }^\text{BP}$ $\Big\vert$ $\overbrace{\ \ \text{8 bits}\ \ \ \vert\ \ \ \text{8 bits}\ \ }^\text{SP}$

• Stride register

  $\overbrace{\ \ \text{4 bits}\ \ \ }^\text{STRIDE}$

RealQ16s core registers

15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00 (bit position) Main registers A $\Big\}$Accumulator AL AH B $\Big\}$Base BL BH C $\Big\}$Count CL CH D $\Big\}$Data DL DH Programming registers IP Instruction pointer SP Stack pointer BP Frame (base) pointer   STRIDE Counter increment