Description: Apple II+ Mini-Assembler (4 of 4)
Header: Apple II+ Mini-Assembler (4 of 4)


 This article last reviewed: 21 September 1984

 08AA: AD 00 02          LDA IN       ;GET CHAR
 08AD: C9 AO             CMP #$AO     ;ASCII SPACE?
 08AF: FO 13             BEQ SPACE    ;YES
 08B1: C8                INY
 08B2: C9 A4             CMP #$A4     ;ASCII '$' IN COL 1?
 08B4: FO 92             BEQ FKMON    ;YES,SIMULATE MONITOR
 08B6: 88                DEY          ;NO, BACKUP A CHAR
 08B7: 20 A7 FF          JSR GETNUM   ;GET A NUMBER
 08BA: C9 93             CMP #$93     ;':' TERMINATOR?
 08BC: DO D5     ERR4    BNE ERR2     ;NO, ERR
 08BE: 8A                TXA
 08BF: FO D2             BEQ ERR2     ;NO ADDR PRECEDING COLON
 08C1: 20 78 FE          JSR A1PCLP   ;MOVE ADDR TO PCL, PCH
 08C4: A9 03     SPACE   LDA #$03     ;COUNT OF CHAR IN MNEMONIC
 08C6: 85 3D             STA A1H
 08C8: 20 EF 09  NXTMN   JSR GETNSP   ;GET 1ST MNEMONIC CHARACTER
 08CB: OA                ASL A
 08CC: E9 BE             SBC #$BE     ;SUBTRACT OFFSET
 08CE: C9 C2             CMP #$C2     ;LEGAL CHARACTER?
 08DO: 90 C1             BCC ERR2     ;NO
 08D2: OA                ASL A        ;COMPRESS-LEFT JUSTIFY
 08D3: OA                ASL A
 08D4: A2 04             LDX #$04
 08D6: 0A        NXTM2   ASL A        ;DO 5 TRIPLE WORD SHIFTS
 08D7: 26 42             ROL A4L
 08D9: 26 43             ROL A4H
 08DB: CA                DEX
 08DC: 10 F8             BPL NXTM2
 08DE: C6 3D             DEC A1H      ;DONE WITH 3 CHAR?
 08EO: FO F4             BEQ NXTM2    ;YES BUT DO 1 MORE SHIFT
 08E2: 10 E4             BPL NXTMN    ;NO
 08E4:                   *
 08E4: A2 05             LDX #$05     ;5-CHAR ADDRESSING MODE
 0836: 20 3F 09  FORM2   JSR GETNSP   ;GET 1ST CHAR OF ADDRESS
 08E9: 84 34             STY YSAV
 08EB: DD B4 F9          CMP CHAR1,X  ;1ST CHAR MATCH PATTERN?
 08EE: DO 13             BNE FORM3    ;NO
 08FO: 20 3F 09          JSR GETNSP   ;YES, GET 2ND CHAR
 08F3: DD BA F9          CMP CHAR2,X  ;MATCHES SECOND HALF?
 08F6: FO ON             BEQ FORM5    ;YES
 08F8: BD BA F9          LDA CHAR2,X  ;NO, IS 2ND HALF ZERO?
 08FB: FO 07             BEQ FORM4    ;YES
 08FD: C9 A4             CMP #$A4     ;NO 2ND HAL OPTIONAL?
 08FF: FO 03             BEQ FORM4    ;YES
@L 0901: A4 34             LDY YSAV
 0903: 18        FORM3   CLC          ;CLEAR CARRY NO MATCH
 0904: 88        FORM4   DEY          ;BACK UP ONE CHARACTER
 0905: 26 44     FORM5   ROL FMT      ;FORM FORMAT BYTE
 0907: EO 03             CPX #$03     ;TIME TO CHECK FOR ADDRESS
 0909: DO OD             BNE FORM7    ;NO
 090B: 20 A7 FF          JSR GETNUM   ;YES
 090E: A5 3F             LDA A2H
 0910: FO 01             BEQ FORM6    ;HIGH ORDER BYTE ZERO
 0912: E8                INX          ;NO, INCR FOR 2-BYTE
 0913: 86 35     FORM6   STX L        ;STORE LENGTH
 0915: A2 03             LDX #$03     ;RELOAD FORMAT INDEX
 0917: 88                DEY          ;BACKUP A CHARACTER
 0918: 86 3D     FORM7   STX A1H      ;SAVE INDEX
 091A: CA                DEX          ;DONE WITH FORMAT CHECK?
 091B: 10 C9             BPL FORM2    ;NO
 091D: A5 44             LDA FMT      ;YES PUT LENGTH
 091F: OA                ASL A        ;IN LOW BITS
 0920: OA                ASL A
 0921: 05 35             ORA L
 0923: C9 20             CMP #$20
 0925: BO 06             BCS FORM8    ;ADD $ IF NONZERO LENGTH
 0927: A6 35             LDX L        ;AND DON'T ALREADY HAVE IT
 0929: FO 02             BEQ FORM8
 092B: 09 80             ORA #$80
 092D: 85 44     FORM8   STA FMT
 092F: 84 34             STY YSAV
 0931: B9 00 02          LDA IN,Y     ;GET NEXT NONBLANK
 0934: C9 BB             CMP #$BB     ;';' START OF COMMENT
 0936: FO 04             BEQ FORM9    ;YES
 0938: C9 8D             CMP #$8D     ;A CARRIAGE RETURN ?
 093A: DO 80             BNE ERR4     ;NO, ERR
 093C: 4C 67 08  FORM9   JMP TRYNEXT
 093F:                   *
 093F: B9 OO 02  GETNSP  LDA IN,Y
 0942: C8                INY
 0943: C9 AO             CMP #$AO     ;GET NEXT NON BLANK CHAR
 0945: FO F8             BEQ GETNSP
 0947: 60                RTS



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