source: xtideuniversalbios/trunk/Assembly_Library/Inc/Delay.inc @ 287

; Project name  :   Assembly Library
; Description   :   Delay macros.
%ifndef DELAY_INC
%define DELAY_INC

;--------------------------------------------------------------------
; Clears prefetch queue by jumping to next instruction.
; This delays much more than nop instruction of fast systems.
;
; JMP_DELAY
;   Parameters
;       Nothing
;   Returns:
;       Nothing
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
%macro JMP_DELAY 0
    jmp     SHORT %%NextInstruction
%%NextInstruction:
%endmacro


;--------------------------------------------------------------------
; Mimimun delays (without fetching) with some CPU architectures:
;   8088/8086:  17 cycles for jump + 5 cycles for last comparison
;   286:        10 cycles for jump + 4 cycles for last comparison
;   386:        13 cycles for jump + ? cycles for last comparison
;   486:         7 cycles for jump + 6 cycles for last comparison
;
; LOOP instruction uses two bytes so aligned fetching will require:
;   8088:       8 cycles (two BYTE reads)
;   8086:       4 cycles (one WORD read)
;   286:        2 cycles + wait states (usually 1)
;   386:        ?
;   486:        Fetched only once to internal cache
;
; DELAY_WITH_LOOP_INSTRUCTION_NA    ; No JUMP_ALIGN
; DELAY_WITH_LOOP_INSTRUCTION
;   Parameters
;       CX:     Loop iterations (0 is maximum delay with 65536 iterations)
;   Returns:
;       CX:     Zero
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
%macro DELAY_WITH_LOOP_INSTRUCTION_NA 0
%%StartOfLoop:
    loop    %%StartOfLoop
%endmacro

%macro DELAY_WITH_LOOP_INSTRUCTION 0
ALIGN JUMP_ALIGN
%%StartOfLoop:
    loop    %%StartOfLoop
%endmacro


%endif ; DELAY_INC