source: xtideuniversalbios/trunk/Assembly_Library/Src/Time/TimerTicks.asm@ 617

; Project name  :   Assembly Library
; Description   :   Functions for system timer related operations.

;
; XTIDE Universal BIOS and Associated Tools
; Copyright (C) 2009-2010 by Tomi Tilli, 2011-2013 by XTIDE Universal BIOS Team.
;
; This program is free software; you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation; either version 2 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
; GNU General Public License for more details.
; Visit http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
;

; With a PIT input clock of 1193181.6666... Hz and a maximum
; 16 bit divisor of 65536 (if PIT programmed with 0) we get:
;
; Clock / Divisor = ~18.2065 ticks per second
; Clock * SecondsPerMinute / Divisor = ~1092 ticks per minute
; Clock * SecondsPerHour / Divisor = ~65543 ticks per hour
;
; Since 65543 can't fit in a 16 bit register we use the
; maximum possible instead and disregard the last ~8 ticks.

TICKS_PER_HOUR          EQU     65535
TICKS_PER_MINUTE        EQU     1092
TICKS_PER_SECOND        EQU     18


; Section containing code
SECTION .text

;--------------------------------------------------------------------
; TimerTicks_GetHoursToAXandRemainderTicksToDXfromTicksInDXAX
; TimerTicks_GetMinutesToAXandRemainderTicksToDXfromTicksInDX
; TimerTicks_GetSecondsToAXandRemainderTicksToDXfromTicksInDX
;   Parameters
;       DX(:AX):    Timer ticks to convert
;   Returns:
;       AX:         Hours, minutes or seconds
;       DX:         Remainder ticks
;   Corrupts registers:
;       CX
;--------------------------------------------------------------------
%ifndef EXCLUDE_FROM_XUB
%ifndef EXCLUDE_FROM_XTIDECFG
ALIGN JUMP_ALIGN
TimerTicks_GetHoursToAXandRemainderTicksToDXfromTicksInDXAX:
    mov     cx, TICKS_PER_HOUR
    div     cx      ; Divide DX:AX by CX, Hours to AX, remainder ticks to DX
    ret
%endif ; EXCLUDE_FROM_XTIDECFG

ALIGN JUMP_ALIGN
TimerTicks_GetMinutesToAXandRemainderTicksToDXfromTicksInDX:
    xor     ax, ax
    xchg    ax, dx  ; Ticks now in DX:AX
    mov     cx, TICKS_PER_MINUTE
    div     cx      ; Divide DX:AX by CX, Minutes to AX, remainder ticks to DX
    ret
%endif ; EXCLUDE_FROM_XUB

%ifndef EXCLUDE_FROM_XUB OR EXCLUDE_FROM_XTIDECFG
ALIGN JUMP_ALIGN
TimerTicks_GetSecondsToAXandRemainderTicksToDXfromTicksInDX:
    ; This procedure can handle at most 4607 ticks in DX (almost 256 seconds)
    ; More than 4607 ticks will generate a divide overflow exception!
    xchg    ax, dx  ; Ticks now in AX
    mov     cl, TICKS_PER_SECOND
    div     cl      ; Divide AX by CL, Seconds to AL, remainder ticks to AH
    xor     dx, dx
    xchg    dl, ah  ; Seconds in AX, remainder in DX
    ret
%endif


%ifdef EXCLUDE_FROM_XUB
    %ifndef MODULE_BOOT_MENU
        %define EXCLUDE
    %endif
%endif
;--------------------------------------------------------------------
; TimerTicks_GetSecondsToAXfromTicksInDX
;   Parameters
;       DX:         Timer ticks to convert
;   Returns:
;       AX:         Seconds
;   Corrupts registers:
;       DX
;--------------------------------------------------------------------
%ifndef EXCLUDE ; 1 of 3
ALIGN JUMP_ALIGN
TimerTicks_GetSecondsToAXfromTicksInDX:
    mov     ax, 3600    ; Approximately 65536 / (Clock / Divisor)
    mul     dx
    xchg    dx, ax
    ret
%endif


;--------------------------------------------------------------------
; First tick might take 0...54.9 ms and remaining ticks
; will occur at 54.9 ms intervals. Use delay of two (or more) ticks to
; ensure at least 54.9 ms timeout.
;
; TimerTicks_InitializeTimeoutFromAX
;   Parameters:
;       AX:         Timeout ticks (54.9 ms) before timeout
;       DS:BX:      Ptr to timeout variable WORD
;   Returns:
;       [DS:BX]:    Initialized for TimerTicks_SetCarryIfTimeoutFromDSBX
;   Corrupts registers:
;       AX
;--------------------------------------------------------------------
%ifndef EXCLUDE ; 2 of 3
ALIGN JUMP_ALIGN
TimerTicks_InitializeTimeoutFromAX:
    mov     [bx], ax                    ; Store timeout ticks
    call    TimerTicks_ReadFromBdaToAX
    add     [bx], ax                    ; [bx] now contains end time for timeout
    ret
%endif


;--------------------------------------------------------------------
; TimerTicks_GetTimeoutTicksLeftToAXfromDSBX
;   Parameters:
;       DS:BX:      Ptr to timeout variable WORD
;   Returns:
;       AX:         Number of ticks left before timeout
;       CF:         Set if timeout
;                   Cleared if time left
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
%ifndef EXCLUDE ; 3 of 3
ALIGN JUMP_ALIGN
TimerTicks_GetTimeoutTicksLeftToAXfromDSBX:
    push    dx
    mov     dx, [bx]
    call    TimerTicks_ReadFromBdaToAX
    xchg    ax, dx
    sub     ax, dx      ; AX = End time - current time
    pop     dx
    ret
%endif

%undef EXCLUDE


;--------------------------------------------------------------------
; TimerTicks_GetElapsedToAXandResetDSBX
;   Parameters
;       DS:BX:      Ptr to WORD containing previous reset time
;   Returns:
;       AX:         54.9 ms ticks elapsed since last reset
;       [DS:BX]:    Reset to latest time
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
%ifndef EXCLUDE_FROM_XUB OR EXCLUDE_FROM_XTIDECFG
ALIGN JUMP_ALIGN
TimerTicks_GetElapsedToAXandResetDSBX:
    call    TimerTicks_ReadFromBdaToAX
    push    ax
    sub     ax, [bx]
    pop     WORD [bx]           ; Latest time to [DS:BX]
    ret
%endif


;--------------------------------------------------------------------
; TimerTicks_GetElapsedToAXfromDSBX
;   Parameters
;       DS:BX:      Ptr to WORD containing previous update time
;   Returns:
;       AX:         54.9 ms ticks elapsed since initializing [DS:BX]
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
%ifndef EXCLUDE_FROM_XUB OR EXCLUDE_FROM_XTIDECFG
ALIGN JUMP_ALIGN
TimerTicks_GetElapsedToAXfromDSBX:
    call    TimerTicks_ReadFromBdaToAX
    sub     ax, [bx]
    ret
%endif


;--------------------------------------------------------------------
; TimerTicks_ReadFromBdaToAX
;   Parameters
;       Nothing
;   Returns:
;       AX:     System time in 54.9 ms ticks
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
%ifdef EXCLUDE_FROM_XUB
    %ifndef MODULE_BOOT_MENU
        %define EXCLUDE
    %endif
%endif

%ifndef EXCLUDE
ALIGN JUMP_ALIGN
TimerTicks_ReadFromBdaToAX:
    push    ds

    LOAD_BDA_SEGMENT_TO ds, ax
    mov     ax, [BDA.dwTimerTicks]  ; Read low WORD only

    pop     ds
    ret
%endif
%undef EXCLUDE