RealQ16s:Provisional register listing

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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
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]
RealQ16s core registers
15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00 (bit position)
Main registers
A [ilmath]\Big\} [/ilmath]Accumulator
B [ilmath]\Big\} [/ilmath]Base
C [ilmath]\Big\} [/ilmath]Count
D [ilmath]\Big\} [/ilmath]Data
Programming registers
IP Instruction pointer
SP Stack pointer
BP Frame (base) pointer
  STRIDE Counter increment