0100 ; CONSOLE KEY EXPANDER›0110 ; BY MATT LOVELESS AND MIKE EGGERS›0120 ; (c) 1987, ANTIC PUBLISHING›0130 ; EQUATES›0140 CONSOL = $D01F  ;CONSOLE BUTTONS›0150 SKSTAT = $D20F  ;SERIAL PORT/KEYBOARD STATUS›0160 VALRTRN = 212   ;LOCATION TO STORE USR RETURN VALUE›0170 SETVBV = $E45C  ;SET VBI VECTOR›0180 SYSVBV = $E45F  ;SYSTEM VBI›0190 XITVBV = $E462  ;EXIT VBI›0200 ;›0210     *=  $0600›0220     LDA #$00›0230     STA FLAG    ;ZERO THE FLAG›0240     PLA ›0250     BNE INIT›0260 ;›0270     RTS ›0280 INIT›0290     TAX ›0300     PLA         ;DISCARD HIGH BYTE AWAY›0310     PLA         ;GET LOW BYTE›0320     STA BUTTON  ;SAVE IT›0330     DEX         ;COMPENSATE FOR REMOVING FIRST ARGUMENT›0340     BEQ GETVBI  ;IF ALL PARAMETERS ARE OFF THEN BRANCH›0350 LOOP1›0360     PLA         ;REMOVE BAD›0370     PLA         ;VALUES WHICH›0380     DEX         ;MIGHT OCCUR›0390     BNE LOOP1   ;IN THE USR CALL›0400 ;›0410 GETVBI›0420     BIT BUTTON›0430     BEQ VBIOFF  ;OPTION #0›0440 ;›0450     BMI VBION   ;OPTION #128›0460 ;›0470 ;OPTION #1›0480 ;›0490     LDA #$01›0500     STA FLAG›0510 ;›0520 VBION›0530     LDA #BUTTON/256 ;HIGH BYTE FOR USR RETURN›0540     STA VALRTRN+1›0550     LDA #BUTTON&255 ;LOW BYTE›0560     STA VALRTRN›0570 ;  GRAB VBI›0580     LDX #VBI/256 ;HIGH BYTE›0590     LDY #VBI&255 ;LOW BYTE›0600     LDA #$07    ;DEFERRED VBI›0610     JSR SETVBV›0620     LDA #$00›0630     STA BUTTON›0640     RTS ›0650 ;›0660 VBIOFF›0670     LDA #CONSOL/256 ;HIGH BYTE FOR USR›0680     STA VALRTRN+1›0690     LDA #CONSOL&255 ;LOW BYTE›0700     STA VALRTRN›0710     LDX #XITVBV/256 ;HIGH BYTE›0720     LDY #XITVBV&255 ;LOW BYTE›0730     LDA #$07    ;DEFERRED VBI›0740     JMP SETVBV  ;ITS RTS WILL RETURN TO CARTRIDGE›0750 ;›0760 ; THE DEFERRED VBI VECTOR POINTS›0770 ; HERE.›0780 ;›0790 VBI›0800     LDA SKSTAT›0810     AND #$08    ;"AND-OUT" ALL BUT BIT-3 (SHIFT KEY)›0820     ORA CONSOL  ;OR, IN CONSOLE KEYS›0830     EOR #$0F    ;SWITCH THE LOWER NIBBLE.›0840     LDX FLAG›0850     BNE ZERO    ;ARE WE IN LATCHED MODE?›0860 ;---YES›0870     TAX         ;COPY A-REG INTO X-REG›0880     AND #$F7    ;AND OUT SHIFT VALUE›0890     BEQ EXIT    ;IF NO CONSOLE KEYS THEN EXIT›0900 ;›0910     TXA         ;ELSE RETURN ORIGINAL VALUE›0920     JMP STORE›0930 ZERO›0940     TAX ›0950     AND #$F7    ;"AND-OUT" SHIFT VALUE›0960     BEQ STORE   ;IF NO CONSOLE KEYS THEN STORE A ZERO›0970 ;›0980     TXA         ;OTHERWISE STORE THE ORIGINAL VALUE›0990 ;›1000 STORE›1010     STA BUTTON›1020 EXIT›1030     JMP XITVBV›1040 ;›1050 FLAG›1060     .BYTE 0›1070 BUTTON›1080     .BYTE 0›1090 ;›1100     .END ›