VersaLogic STD32 VL-1225, Справочное руководство

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6-4
VL-1225/6 Analog Input/Output Board
004C isr: ;INTERRUPT SERVICE ROUTINE
004C 50 push ax ;Save CPU registers
004D 51 push cx
004E 52 push dx
004F 1E push ds
0050 B8 ---- R mov ax,data ;Set data segment register
0053 8E D8 mov ds,ax
;Read A/D results
0055 BA 0305 mov dx,idhigh ;Read Data High register first
0058 EC in al,dx
0059 8A E0 mov ah,al ;Mask off unused high-order bits
005B 80 E4 03 and ah,03h ;(Use ‘ah,07h’ for 11 bit mode)
005E BA 0304 mov dx,idlow ;Read Data Low register second
0061 EC in al,dx
0062 signex: ;Sign extend to fill 16-bit register
;The following 3 instructions are
;optional. They are used in
;two’s complement mode only.
0062 B1 06 mov cl,6 ;Shift count (use ‘cl,5’ for 11-bit mode)
0064 D3 E0 sal ax,cl ;Shift AD10 or AD11 into bit position D7
0066 D3 F8 sar ax,cl ;Shift it back, extending sign
0068 A3 0000 R mov value,ax ;Store results into variable
006B C7 06 0002 R FFFF mov done,0ffffh ;Set flag indicating that ISR has ex-
ecuted
;Additional processing code is
;inserted here if desired.
;This could include mathematic
;manipulation, data storage,
;limit checks, etc.
0071 isr_exit:
0071 BA FF22 mov dx,eoi ;Issue a Non-Specific End-Of-Interrupt
0074 B8 8000 mov ax,8000h ;command to 80188 interrupt controller
0077 EF out dx,ax
0078 1F pop ds ;Restore CPU registers
0079 5A pop dx
007A 59 pop cx
007B 58 pop ax
007C CF iret ;Return to interrupted program
007D code ends
end main
Software Examples – Interrupt Mode Analog Input