C/C++ Users Group Library 1996 July/C-C++ Users Group Library July 1996.iso/listings/v_10_12/1012047a

Text File | 1992-10-08 | 3.9 KB | 211 lines

page ,132

; masm tisr ; >err
    .286p
.xlist
include ..\..\include\bogus.inc
.list


Words struc
LoWord dw ?
HiWord dw ?
Words ends

EOI equ 020h            ; EOI command for PIC

INTA00 equ 020h         ; Master PIC control
INTA01 equ 021h         ; Master PIC mask register
INT_MASTER_0 equ 08h        ; Master PIC INT number

INTB00 equ 0A0h         ; Slave PIC control
INTB01 equ 0A1h         ; Slave PIC mask register
INT_SLAVE_0 EQU 70h        ; Slave PIC INT number

;
; Set variables for our interrupt number
;
ife (FAKE_IRQ GE 8)
INT_DEV equ (INT_MASTER_0+(FAKE_IRQ AND 7))
PIC00 equ INTA00
PIC01 equ INTA01
else
INT_DEV equ (INT_SLAVE_0+(FAKE_IRQ AND 7))
INT_MASK equ 1 SHL (FAKE_IRQ AND 7)
PIC00 equ INTB00
PIC01 equ INTB01
endif

page
CONST SEGMENT DWORD PUBLIC 'DATA'
sdNoBogus db 'I do not see the bogus device.',0dh,0ah,'$'
sdPrompt db 0Dh,0Ah,'S)tart, or Q)uit: ','$'
sdCRLF    db 0Dh,0Ah,'$'
sdDot    db '.','$'

CONST ENDS

DATA SEGMENT DWORD PUBLIC 'DATA'
dwCount1 dw 0
dwCount2 dw 0
lpPrevISR dd 0            ; address of prior ISR
fStopping db 0            ; TRUE when stopping
DATA ENDS

STACK SEGMENT DWORD STACK 'STACK'
    db    512 dup (?)
STACK ENDS

DGroup GROUP CONST,DATA,STACK

page

;IP    IntSvcRtn - The Interrupt Service Routine
;
;    WARNINGS
;
;    NOTES
;        This ISR generally increments an interrupt count (dwCount1)
;        and re-arms the device.
;
;        If the "fStopping" flag is set, the device is not re-armed.
;

FIXED_TEXT SEGMENT PARA PUBLIC 'CODE'
segData1    dw    DGroup
    assume    CS:FIXED_TEXT,DS:NOTHING
IntSvcRtn proc far
    push    ax
    push    dx
    push    ds
    mov    ds,segData1
    assume    ds:DGroup
    inc    dwCount1
    mov    al,NOT FAKE_CTL_EOI
    mov    dx,FAKE_PORT
    out    dx,al            ; send EOI to device
    mov    al,EOI
    out    PIC00,al        ; send EOI to PIC
ife (PIC00 EQ INTA00)
    out    INTA00,al        ; send EOI to master PIC, too
endif
    cmp    fStopping,0        ; exiting?
    jnz    isr9            ; if so, then don't restart
    mov    al,NOT FAKE_CTL_START
    mov    dx,FAKE_PORT
    out    dx,al            ; restart I/O
isr9:
    pop    ds
    assume    ds:NOTHING
    pop    dx
    pop    ax
    iret
IntSvcRtn endp

FIXED_TEXT ENDS

page
;IP    __main - program entry point
;
;    NOTES
;        The user is prompted to S)tart or Q)uit the program.  If
;        "S" is selected, the programs enables interrupts and arms
;        the device, printing out a dot each time the device interrupts.
;

_TEXT SEGMENT PARA PUBLIC 'CODE'
segData2    dw    DGroup
segFixed    dw    FIXED_TEXT
    assume    cs:_TEXT,ds:NOTHING

__main label far
    mov    ds,segData2        ; Initialize default data segment
    assume    ds:DGroup

    mov    dx,FAKE_PORT
    in    al,dx            ; Is the bogus device present ?
    or    al,al
    jns    ml0            ; skip if so
    mov    dx,OFFSET DGroup:sdNoBogus
    mov    ah,9
    int    21h            ; else print error message
    mov    ax,4C01h
    int    21h            ; and exit

ml0:
    mov    ax,3500h+INT_DEV
    cli
    int    21h            ; Query the current ISR
    mov    lpPrevISR.LoWord,bx
    mov    lpPrevISR.HiWord,es ; Save it

    mov    dx,OFFSET FIXED_TEXT:IntSvcRtn
    push    ds
    mov    ds,segFixed
    assume    ds:NOTHING
    mov    ax,2500h+INT_DEV
    int    21h            ; Set our ISR
    pop    ds
    assume    ds:DGroup
    sti

    mov    dx,OFFSET DGroup:sdPrompt
    mov    ah,9
    int    21h            ; "S)tart or Q)uit

ml1:
    mov    dl,0FFh
    mov    ah,6
    int    21h            ; read from console, nowait
    jz    ml3
    or    al,40h
    cmp    al,'q'
    je    ml8            ; skip if "Q" pressed
    cmp    al,'s'
    jne    ml3            ; skip if "S" not pressed
    cli
    in    al,PIC01        ; unmask the interrupt
    and    al,NOT INT_MASK
    out    PIC01,al
    sti
    mov    al,NOT FAKE_CTL_START
    mov    dx,FAKE_PORT
    out    dx,al            ; start device I/O
ml3:
    mov    ax,dwCount1
    cmp    ax,dwCount2
    je    ml4            ; skip if the count of interrupts unchanged
    mov    dwCount2,ax
    mov    dx,OFFSET DGroup:sdDot
    mov    ah,9
    int    21h            ; else, display a dot
ml4:
    jmp    ml1            ; loop for more

ml8:
    mov    fStopping,1        ; Tell the ISR to stop
    mov    dx,FAKE_PORT
ml9:
    in    al,dx
    rcr    al,1
    jnc    ml9            ; loop while busy

    cli
    in    al,PIC01
    or    al,INT_MASK
    out    PIC01,al        ; mask the interrupt level
    sti

    push    ds
    lds    dx,lpPrevISR
    assume    ds:NOTHING
    mov    ax,2500h+INT_DEV
    int    21h            ; restore the previous ISR
    pop    ds
    assume    ds:DGroup
    mov    ax,4C00h
    int    21h            ; exit
_TEXT ENDS

    end    __main