C/C++ Users Group Library 1996 July/C-C++ Users Group Library July 1996.iso/vol_300/330_03/tsktim.asm

Assembly Source File | 1990-10-10 | 13.5 KB | 665 lines

;
;    --- Version 2.2 90-10-12 10:46 ---
;
;    CTask - Timer interrupt handler (IBM specific)
;
;    Public Domain Software written by
;        Thomas Wagner
;        Ferrari electronic Gmbh
;        Beusselstrasse 27
;        D-1000 Berlin 21
;        Germany
;
;    NOTE: Logic in this module has been changed to accommodate two
;          different ways to handle chaining to the original INT 8
;          entry in version 1.2.
;
;    CAUTION: This module can only be installed in the primary kernel.
;         It is not ROMable.
;
;    For non-IBM applications, you have to completely replace
;    this module and write your own.
;    You should be able to use this module at least as a model
;    by throwing out about 80%, mainly the initialization
;    and interrupt chaining stuff. All you really need is the
;    tsk_timer_counter increment, and the ticker processing,
;    which can be left unchanged. The section enclosed by
;    IF INT8_EARLY most likely is the one you should use as
;    reference, since you will usuallly not have other routines
;    chained to the timer tick in an embedded system.
;
    name    tsktim
;
    include    tsk.mac
    include    tskdeb.h
;
    .tsk_model
;
    Pubfunc    tsk_install_timer
    Pubfunc    tsk_remove_timer
    IF    NOT INT8_EARLY
    Pubfunc    tsk_chain_timer
    ENDIF
;
    extrn    sched_int: far
    Globext    inc_counter
    Globext    set_flag
;
    extrn    tsk_key_avail: byte
    extrn    tsk_glob_rec: byte
    extrn    tsk_timer_counter:word
    extrn    tsk_instflags: word
    IF    NOT INT8_EARLY
    extrn    tsk_int8_counter:word
    ENDIF
;
    IF    DEBUG AND DEB_FLASHERS
    Locext    tsk_inccdis
    extrn    tsk_debflash: word
    extrn    tsk_dtposn: dword
    ENDIF
;
;
STACKSIZE    =    128    ; local stack size (words)
;
timer    equ    40h            ; 8253 timer base I/O address
inta00    equ    20h            ; 8259 int controller base
eoi    equ    20h            ; unspecific EOI
;
intseg    segment at 0
;
        org    8*4
tintofs        dw    ?        ; timer interrupt entry
tintseg        dw    ?

intseg    ends
;
biosdataseg    segment at 40h
    org    1ah
kbdptr1    dw    ?
kbdptr2    dw    ?
biosdataseg    ends
;
    IF    FAR_STACKS
ctask_stacks    segment word public 'CTASK_STACKS'
    ELSE
    .tsk_data
    ENDIF
;
    dw    STACKSIZE dup(?)
local_stack    label    word
;
    IF    FAR_STACKS
ctask_stacks    ends
    .tsk_data
    ENDIF
;
divisor        dw    ?
timflag        dw    ?
timcnt        dw    ?
sys_ticks    dw    ?
;
    .tsk_edata
    .tsk_code
;
tsk_dgroup    dw    @CTASK_DATA
;
    IF    FAR_STACKS
stackseg    dw    SEG ctask_stacks
    ELSE
stackseg    equ    <tsk_dgroup>
    ENDIF
;
timer_save    label    dword        ; in CSEG to allow addressing
tsofs        dw    ?
tsseg        dw    ?
;
r_ss        dw    ?
r_sp        dw    ?
in_timer    db    0
;
;----------------------------------------------------------------------
;
     IF    NOT INT8_EARLY
;
;    Timer interrupt handler, late INT 8 processing
;
;    Normal timer tick. The tick counter is incremented, and
;    the interrupt controller is checked for other pending interrupts.
;    If the timer tick occurred during processing of another interrupt,
;    we may not call the scheduler, since this would delay the
;    interrupt handler.
;
;    Note that an EOI is issued here to allow interrupts to occur
;    during further processing. The original INT 8 handler will be
;    chained to from a special task. The reason behind this is that
;    some TSR's link into the timer interrupt and may do some lengthy
;    processing there. To allow the TSR to be preempted, we must use
;    a task for the INT 8 processing.
;
@timer_int_late    proc    far
;
;    first, check for overrun. If we're already processing a tick,
;    we simply ignore this one. That's not that great a way to
;    react, but anything else would easily mess things up, and we're
;    already in trouble anyway if this should happen.
;
    cmp    cs:in_timer,0
    je    timer_ok
    push    ax
    mov    al,eoi            ; issue EOI
    out    inta00,al
    pop    ax
    iret
;
;    Not a second interrupt, continue processing. First, set the
;    in_timer marker, and switch to our local stack.
;
timer_ok:
    inc    cs:in_timer
    mov    cs:r_ss,ss
    mov    cs:r_sp,sp
    mov    ss,cs:stackseg
    mov    sp,offset local_stack
    sti
    cld
    push    ax
    push    ds
    mov    ds,cs:tsk_dgroup
;
    IF    DEBUG AND DEB_FLASHERS
    cmp    tsk_debflash,0
    je    debdd0
    mov    ax,DEBP_CNTTICK
    call    tsk_inccdis
debdd0:
    ENDIF
;
    push    es            ; save other regs
    push    bx
    push    cx
    push    dx
    push    si
    push    di
    push    bp
    callp    inc_counter,<<ds,#tsk_timer_counter>> ; increase timer tick counter
;
;    Now the timer counter is decremented. If it is zero,
;    we must chain to the original INT 8, so the counter for
;    the chain task is incremented.
;
    dec    timcnt            ; decrement tick count
    jnz    no_pass            ; pass on this int if zero
;
    mov    ax,sys_ticks
    mov    timcnt,ax        ; re-init tick counter
;
    callp    inc_counter,<<ds,#tsk_int8_counter>>
;
;    Now we decrement all installed tick counters
;
no_pass:
    les    bx,tsk_glob_rec.ticker_chain
;
count_dec:
    mov    ax,es
    or    ax,bx
    jz    tick_ready
    mov    ax,es:ticklo[bx]
    or    ax,es:tickhi[bx]
    jz    count_next
    sub    es:ticklo[bx],1
    sbb    es:tickhi[bx],0
count_next:
    les    bx,es:ticknext[bx]
    jmp    count_dec
;
;    Now check the BIOS keyboard buffer.
;    If there are chars in the buffer, set the tsk_key_avail flag
;    to wake up tasks waiting for the keyboard. This check is required
;    to find out about keyboard stuffers placing characters directly
;    into the keyboard buffer.
;
tick_ready:
    mov    ax,SEG biosdataseg
    mov    es,ax
    assume    es:biosdataseg
    mov    ax,es:kbdptr1
    cmp    ax,es:kbdptr2
    assume    es:@CTASK_DATA
    je    tick_exit
    callp    set_flag,<<ds,#tsk_key_avail>>
;
tick_exit:
    pop    bp
    pop    di
    pop    si
    pop    dx
    pop    cx
    pop    bx
    pop    es
;
    cli
    mov    al,eoi            ; issue EOI
    out    inta00,al
    mov    al,0bh            ; access int control reg
    out    inta00,al
    in    al,inta00        ; ints pending?
    or    al,al
    jnz    tim_retn        ; don't schedule if other ints active
    IF    DEBUG AND DEB_FLASHERS
    cmp    tsk_debflash,0
    je    debdda1
    push    bx
    lds    bx,tsk_dtposn
    mov    byte ptr [bx+DEBP_CNTTICK+DEBFLASH_NDIGS*2],'+'
    pop    bx
debdda1:
    ENDIF
    pop    ds
    pop    ax
    mov    ss,cs:r_ss
    mov    sp,cs:r_sp
    dec    cs:in_timer
    jmp    sched_int        ; else schedule
;
tim_retn:
    IF    DEBUG AND DEB_FLASHERS
    cmp    tsk_debflash,0
    je    debdda2
    push    bx
    lds    bx,tsk_dtposn
    mov    byte ptr [bx+DEBP_CNTTICK+DEBFLASH_NDIGS*2],'-'
    pop    bx
debdda2:
    ENDIF
    pop    ds
    pop    ax
    mov    ss,cs:r_ss
    mov    sp,cs:r_sp
    dec    cs:in_timer
    iret
;
@timer_int_late    endp
;
    ENDIF
;
;----------------------------------------------------------------------
;
     IF    NOT INT8_LATE
;
;    Timer interrupt handler, early INT 8 processing
;
;    With this interrupt handler, the original INT 8 is chained to
;    directly, before calling the scheduler.
;
;    This avoids compatibility problems with TSR's that do strange
;    things in the timer tick, but it may lead to problems within
;    CTask, should the strange TSR decide to loop in the INT 8 handler,
;    or even to never return. Oh well, you can't please all TSR's all
;    of the time...
;
@timer_int_early    proc    far
;
    cld
    push    ax
    push    ds
    mov    ds,cs:tsk_dgroup
;
    IF    DEBUG AND DEB_FLASHERS
    cmp    tsk_debflash,0
    je    debdd1
    mov    ax,DEBP_CNTTICK
    call    tsk_inccdis
debdd1:
    ENDIF
;
;    The timer counter is decremented. If it is zero,
;    we chain directly to the original INT 8.
;    Since the local stack is not yet in use,
;    multiple entries into this part are possible.
;
    xor    ah,ah            ; no delayed tick
    dec    timcnt            ; decrement tick count
    jnz    eno_pass
;
    mov    ax,sys_ticks
    mov    timcnt,ax        ; re-init tick counter
;
;    Version 2.1 adds a check for scheduler active here.
;    We may not call the original INT 8 if the scheduler is active,
;    since this would crash the system when the old INT 8 causes
;    a task_wait. See tskasm.asm for a more detailed explanation.
;
    cmp    tsk_glob_rec.in_sched,0
    je    call_oldint
;
    mov    ah,1            ; mark delayed tick
    jmp    short eno_pass
;
call_oldint:
    sti
    pop    ds
    pop    ax
    pushf
    call    cs:timer_save        ; call original INT 8
    push    ax
    push    ds
    mov    ds,cs:tsk_dgroup
    xor    ah,ah            ; no delayed tick
    jmp    short e_pass
;
;    On return from INT 8 processing, or when INT 8 was not chained,
;    processing is pretty much the same as in timer_int_late.
;
eno_pass:
    mov    al,eoi            ; issue EOI when not chained
    out    inta00,al
;
e_pass:
    cli
    cmp    cs:in_timer,0
    je    etimer_ok
    pop    ds
    pop    ax
    iret
;
etimer_ok:
    inc    cs:in_timer
    mov    cs:r_ss,ss
    mov    cs:r_sp,sp
    mov    ss,cs:stackseg
    mov    sp,offset local_stack
    sti
    cld
;
    push    es            ; save other regs
    push    bx
    push    cx
    push    dx
    push    si
    push    di
    push    bp
;
;    If the tick was delayed, we have to notify the tsk_int8 to
;    process an additional tick when there's time.
;
    IF    NOT INT8_EARLY
    or    ah,ah            ; check delay flag
    jz    no_delay
    callp    inc_counter,<<ds,#tsk_int8_counter>>
    ENDIF
;
no_delay:
    callp    inc_counter,<<ds,#tsk_timer_counter>> ; increase timer tick counter
;
;    Now we decrement all installed tick counters
;
    les    bx,tsk_glob_rec.ticker_chain
;
ecount_dec:
    mov    ax,es
    or    ax,bx
    jz    etick_ready
    mov    ax,es:ticklo[bx]
    or    ax,es:tickhi[bx]
    jz    ecount_next
    sub    es:ticklo[bx],1
    sbb    es:tickhi[bx],0
ecount_next:
    les    bx,es:ticknext[bx]
    jmp    ecount_dec
;
;    Now check the BIOS keyboard buffer.
;    If there are chars in the buffer, set the tsk_key_avail flag
;    to wake up tasks waiting for the keyboard. This check is required
;    to find out about keyboard stuffers placing characters directly
;    into the keyboard buffer.
;
etick_ready:
    mov    ax,SEG biosdataseg
    mov    es,ax
    assume    es:biosdataseg
    mov    ax,es:kbdptr1
    cmp    ax,es:kbdptr2
    assume    es:@CTASK_DATA
    je    etick_exit
    callp    set_flag,<<ds,#tsk_key_avail>>
;
etick_exit:
    pop    bp
    pop    di
    pop    si
    pop    dx
    pop    cx
    pop    bx
    pop    es
;
    cli
    mov    al,0bh            ; access int control reg
    out    inta00,al
    in    al,inta00        ; ints pending?
    or    al,al
    jnz    etim_retn        ; don't schedule if other ints active
    mov    ss,cs:r_ss
    mov    sp,cs:r_sp
    pop    ds
    pop    ax
    dec    cs:in_timer
    jmp    sched_int        ; else schedule
;
etim_retn:
    mov    tsk_glob_rec.pretick,1    ; mark that we missed a schedule
    mov    ss,cs:r_ss
    mov    sp,cs:r_sp
    pop    ds
    pop    ax
    dec    cs:in_timer
    iret
;
@timer_int_early    endp
;
    ENDIF
;
;---------------------------------------------------------------------
;
;    Install timer.
;    The scheduler is not called on this first tick.
;
@tim_install    proc    far
;
    push    ax
    push    ds
    push    es
;
    mov    ds,cs:tsk_dgroup
;
    mov    timflag,0        ; signal init ready
    mov    ax,sys_ticks
    mov    timcnt,ax        ; init tick counter
    mov    al,36h
    out    timer+3,al        ; setup to load divisor
    mov    al,byte ptr divisor
    out    timer,al        ; lsb
    mov    al,byte ptr divisor+1
    out    timer,al        ; msb
;
    xor    ax,ax
    mov    es,ax
    assume    es:intseg
;
    IF    INT8_EARLY
    mov    ax,offset @timer_int_early
    ELSE
    mov    ax,offset @timer_int_late
    IF    NOT INT8_LATE
    test    tsk_instflags,IFL_INT8_DIR
    jz    tim_inst_1
    mov    ax,offset @timer_int_early
    ENDIF
    ENDIF
;
tim_inst_1:
    mov    es:tintofs,ax
    mov    es:tintseg,cs
;
    pop    es
    pop    ds
    pop    ax
    jmp    cs:timer_save
;
@tim_install    endp
;
;------------------------------------------------------------------------
;
;       Un-Install timer (wait until system tick count reached).
;    The scheduler is not called while waiting for the tick count.
;
@tim_uninstall    proc    far
;
    push    ax
    push    ds
;
    mov    ds,cs:tsk_dgroup
;
    cli
    dec    timcnt            ; decrement tick count
    jz    uninit            ; go un-install if zero
    mov    al,eoi            ; else just issue EOI
    out    inta00,al
    pop    ds
    pop    ax
    iret
;
;    Uninstall timer int handler
;
uninit:
    mov    timflag,0        ; mark un-install complete
    mov    al,36h            ; setup to load divisor
    out    timer+3,al
    mov    al,0            ; divisor 0 means 65536
    out    timer,al        ; lsb
    out    timer,al        ; msb
;
    push    es
    xor    ax,ax
    mov    es,ax
    assume    es:intseg
    mov    ax,cs:tsofs        ; restore vector
    mov    tintofs,ax
    mov    ax,cs:tsseg
    mov    tintseg,ax
    pop    es
    pop    ds
    pop    ax
    jmp    cs:timer_save        ; pass on interrupt
;
@tim_uninstall    endp
;
;----------------------------------------------------------------------
;
    IF    NOT INT8_EARLY
;
;    void far tsk_chain_timer (void)
;
;       Pass timer tick on to interrupt 8 chain.
;
Localfunc tsk_chain_timer
;
    IF    DEBUG AND DEB_FLASHERS
    cmp    tsk_debflash,0
    je    debdd2
    mov    ax,DEBP_CNTTCHAIN
    call    tsk_inccdis
debdd2:
    ENDIF
    pushf
    cli
    call    cs:timer_save
    ret
;
tsk_chain_timer    endp
;
    ENDIF
;
;
;    void near tsk_install_timer (word divisor, word sys_ticks)
;
;    This routine installs the timer tick int handler.
;    The timer chip is reprogrammed on the next tick.
;
Localfunc tsk_install_timer,<pdivisor: word, psysticks: word>
;
    IFDEF    LOAD_DS
    push    ds
    mov    ds,cs:tsk_dgroup
    ENDIF
;
    mov    ax,pdivisor
    mov    divisor,ax
    mov    ax,psysticks
    mov    sys_ticks,ax
    mov    timflag,1        ; set init-flag
    xor    ax,ax
    mov    es,ax            ; establish addressing for intseg
    assume    es:intseg
;
    mov    ax,tintofs        ; save old timer int addr
    mov    tsofs,ax
    mov    ax,tintseg
    mov    tsseg,ax
    cli
    mov    tintofs,offset @tim_install ; set new timer int addr
    mov    tintseg,cs
    sti
    assume    es:nothing
wait_set:
    cmp    timflag,0        ; wait until timer started
    jne    wait_set
    IFDEF    LOAD_DS
    pop    ds
    ENDIF
    ret
;
tsk_install_timer    endp
;
;
;    void far tsk_remove_timer (void)
;
;    This routine un-installs the timer tick int handler.
;    The timer chip is reprogrammed & the interrupt vector
;    restored when the system tick count reaches zero.
;
Localfunc tsk_remove_timer
;
    IFDEF    LOAD_DS
    push    ds
    mov    ds,cs:tsk_dgroup
    ENDIF
;
    mov    timflag,2        ; set un-init flag for timer

    xor    ax,ax
    mov    es,ax            ; establish addressing for intseg
    assume    es:intseg
;
    cli
    mov    tintofs,offset @tim_uninstall ; set new timer int addr
    mov    tintseg,cs
    sti
    assume    es:nothing
wait_tim:
        sti                             ; just to be safe
    cmp    timflag,0        ; wait until int un-installed
    jne    wait_tim
    IFDEF    LOAD_DS
    pop    ds
    ENDIF
    ret
;
tsk_remove_timer    endp
;
    .tsk_ecode
    end