TITLE 'VBI MODULE'›SUBTTL 'File VBLANK.AMA'›;›; This module creates & invokes a deferred›; vertical blank interrupt routine to monitor the›; console switch status and set flags for screen›; display and printer output when selected›; by the operator.›;›PROC›VBLANKLDA #7     ; Select deferred VBI›LDY #LOW DVBI›LDX #HIGH DVBI›JSR SETVBV›RTS›;›; This is the deferred VBI routine›;›DVBILDA CONSOL›AND #$07›EOR #$07›BNE :DVB2;Switch pressed›LDA DBTIM;Debounce timer›BEQ :EXIT›DEC DBTIM›JMP :EXIT›:DVB2STA CONSAV›LDA DBTIM›BNE :EXIT›LDA #5›STA DBTIM›LDA CONSAV›AND #4›BEQ :DVB4›LDA PROPT  ;OPTION selects printer›EOR #$FF›STA PROPT›:DVB4LDA CONSAV›AND #1›BEQ :EXIT›LDA FREEZE  ;START freezes display›EOR #$FF›STA FREEZE›:EXITJMP XITVBV›EPROC›››