; irq handler for updating vector locations/angles
;
; this uses irq 8 set to the same speed as the vertical retrace so that
; an animation will remain at a smooth/constant speed regardless of the
; machine speed: eg, a 386SX33 will run an animation at the same  speed
; as a 486DX66, only the 386 will skip frames to compensate.all the irq
; really does is "inc traces_past" and this information is used to skip
; frames. if traces_past =1 is 486DX66, =4 is 386 or whatever.  you get
; the idea right?
;
; the irq can operate in real mode or pmode.  just call the appropiate
; routine.  i did this in case you want to add to  the  irq  your  own
; functions for sound or music or whatever.

        .386p

        public set_pmirq
        public reset_pmirq

        public set_rmirq
        public reset_rmirq

        public reset_raster_count
        public time_raster

        public frametime

        include 3d.inc
        include equ.inc

        pmodeirq equ 0  ; you could also use irq 8 for either of these.
        rmodeirq equ 0  ; both can run at the same time even if both=0.

code16  segment para public use16
        assume cs:code16, ds:code16

;ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
rmirq0:                                 ; real mode IRQ0 handler
        push ax ds

; put your real mode irq code here!!!!!
;--------------------------------------



;--------------------------------------

; now my code, this is where i inc that variable
; real mode irq increments protected mode memory location

        mov ax,cs:rfs
        mov ds,ax
        mov si,cs:rfo

        inc word ptr [si]               ; inc traces_past
        inc dword ptr [si+2]            ; inc frame_number

        pop ds
        mov al,20h
        out 20h,al
        pop ax

        iret

rfs     dw ?
rfo     dw ?

transfer_location:
        mov cs:rfs,cx                   ; set protected mode location of
        mov cs:rfo,dx                   ; traces_past in terms of real mode
        ret

code16  ends

code32  segment para public use32
        assume cs:code32, ds:code32

        include pmode.inc

ormirq0 dd ?                            ; old real mode IRQ handler seg:off
opmirq0 dd ?                            ; old protected mode IRQ handler off

pmirq0:                                 ; protected mode IRQ0 handler
        push ds

; put your protected mode irq code here!!!!!
;-------------------------------------------



;-------------------------------------------

; now my code, this is where i inc that variable
; protected mode version is easy!

        inc traces_past
        inc frame_number

        pop ds
        jmp cs:opmirq0                  ; chain to old IRQ0 redirector

set_rmirq:
        mov eax,gs:[rmodeirq*4]         ; save real mode IRQ0 vector
        mov ormirq0,eax

        cli                             ; set IRQ0 to inc variable

        mov word ptr gs:[rmodeirq*4],offset rmirq0  ; set real mode irq
        mov word ptr gs:[(rmodeirq*4)+2],code16

        mov edx,offset traces_past      ; tell real mode irq where traces_past
        add edx,_code32a                ; is in memory (pmode location)
        mov al,dl
        and ax,0fh
        shr edx,4
        mov v86r_cx,dx
        mov v86r_dx,ax

        mov cx,seg transfer_location
        mov dx,offset transfer_location
        int 32h

        sti

        jmp new_timer

reset_rmirq:
        cli

        mov eax,ormirq0                 ; restore old real mode IRQ0 vector
        mov gs:[rmodeirq*4],eax

        sti

        jmp old_timer

set_pmirq:
        xor bl,bl                       ; get protected mode IRQ0 redirector
        call _getirqvect
        mov opmirq0,edx

        cli                             ; set IRQ0 to inc variable

        mov bl,pmodeirq
        mov edx,offset pmirq0
        call _setirqvect                ; set protected mode irq

        sti

        jmp new_timer

reset_pmirq:
        cli

        mov bl,pmodeirq
        mov edx,opmirq0
        call _setirqvect

        sti

        jmp old_timer

new_timer:
        call time_raster

        cli
        mov al,36h
        out 43h,al
        mov ax,frametime               ; set irq 8 time to match raster time
        out 40h,al
        mov al,ah
        out 40h,al
        sti

        ret

old_timer:                             ; reset timer for exit
        cli
        mov al,36h
        out 43h,al

        mov ax,0
        out 40h,al
        out 40h,al

        sti

        ret

reset_raster_count:                    ; reset count before any animation loop
        cli
        mov traces_past,1
        mov frame_number,0
        sti
        ret

frametime dw 0

time_raster:
        cli
        mov dx, input_1        ; input# 1 reg
loop1:
        in al,dx               ; wait for vsync
        test al,8
        jnz loop1
loop2:
        in al,dx
        test al,8
        jz loop2

        mov al,36h             ; reset timer
        out 43h,al
        mov al,0
        out 40h,al
        mov al,0
        out 40h,al
loop3:
        in al,dx               ; wait for vsync
        test al,8
        jnz loop3
loop4:
        in al,dx
        test al,8
        jz loop4

        xor al,al              ; this calculation code courtesy future_crew
        out 43h,al             ; from mental.exe
        in al,40h
        mov ah,al
        in al,40h
        xchg al,ah
        neg ax
        shr ax,1
        mov frametime,ax

        sti
        ret

code32  ends
        end