mirror of
https://github.com/nathanriggs/AppleIIAsm-Collection.git
synced 2024-12-03 18:49:28 +00:00
206 lines
5.2 KiB
Plaintext
206 lines
5.2 KiB
Plaintext
*
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*``````````````````````````````*
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* STRCAT :: STRING CONCATENATE *
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*- -*
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* CONCATENATE TWO STRINGS INTO *
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* A SINGLE STRING STORE WHERE *
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* THE FIRST STRING IS LOCATED. *
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* ADDITIONALLY COPIES CONCAT'D *
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* STRING TO [RETURN]. *
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*- -*
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* CLOBBERS: *
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* *
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* FLAGS: ????---- REG: AXYM *
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*- -*
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* CYCLES: ??? *
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* SIZE: *
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*- -*
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* USAGE: *
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* *
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* LDA #>CATSTR *
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* PHA *
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* LDA #<CATSTR *
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* PHA *
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* LDA #>CATSTR2 *
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* PHA *
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* LDA #<CATSTR2 *
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* PHA *
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* LDA #7 ; MAX SIZE OF CAT *
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* PHA *
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* JSR STRCAT *
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* *
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* CATSTR STR "ABC" *
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* BLANK STR " " *
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* CATSTR2 STR "DEF" *
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*- -*
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* ENTRY *
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* *
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* TOP OF STACK *
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* *
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* LOW BYTE OF RETURN ADDRESS *
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* HI BYTE OF RETURN ADDRESS *
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* MAXIMUM LENGTH OF CONCAT STR *
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* LOW BYTE OF STR2 ADDRESS *
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* HIGH BYTE OF STR2 ADDRESS *
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* LOW BYTE OF STR1 ADDRESS *
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* HIGH BYTE OF STR1 ADDRESS *
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*- -*
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* EXIT *
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* *
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* TOP OF STACK *
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* *
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* LOW BYTE OF RETURN ADDRESS *
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* HI BYTE OF RETURN ADDRESS *
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* *
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* .Y = CLOBBERED; TRASH *
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* .X = LENGTH OF FINAL STRING *
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* .A = 1 IF OVERFLOW, 0 IF NO *
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* [RETURN] = CONCAT'D STRING *
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* [RETLEN] = LENGTH OF NEW STR *
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*- -*
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* ADAPTED FROM LEVANTHAL AND *
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* WINTHROP'S /6502 ASSEMBLY *
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* LANGUAGE ROUTINES/. *
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*,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,*
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*
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STRCAT
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*
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** SAVE RETURN ADDRESS
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*
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PLA
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STA RETADR
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PLA
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STA RETADR+1
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*
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** GET PARAMETERS
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*
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PLA
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STA :MLEN ; MAXIMUM CONCAT LENGTH
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*
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PLA
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STA ADDR2 ; STRING 1 ADDRESS
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PLA ; IN ZERO PAGE
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STA ADDR2+1
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PLA
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STA ADDR1 ; STRING 2 ADDRESS
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PLA ; IN ZERO PAGE
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STA ADDR1+1
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*
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** DETERMINE WHERE TO START
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*
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LDY #0
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LDA (ADDR1),Y ; GET CUR LGTH OF S1, STORE
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STA :S1LEN
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STA :S1IND
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INC :S1IND ; START CONCAT AT END OF S1
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LDA (ADDR2),Y ; GET LENGTH OF S2, STORE
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STA :S2LEN
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LDA #1
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STA :S2IND ; START CONCAT AT BEGIN OF S2
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*
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** DETERMINE NUMBER OF CHAR
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*
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LDA :S2LEN ; GET S2 LENGTH
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CLC
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ADC :S1LEN ; ADD TO LENGTH OF S1
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STA :S3LEN ; STORE CONCAT LENGTH
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BCS :TOOLONG ; BR IF LENGTH > 255
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CMP :MLEN ; CHECK AGAINST MAX LENGTH
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BEQ :LENOK ; BR IF LENGTH < MAX
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BCC :LENOK
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*
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** RESULTING STRING WILL BE TOO LONG SO
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** INDICATE A STRING OVERFLOW, __SOVF = 0FF
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** SET NUMBER OF CHARS TO CONCAT = MLEN - S1LEN
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** SET LENGTH OF STRING 1 TO MAX LENGTH
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*
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:TOOLONG
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LDA #$0FF
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STA :SOVF ; INDICATE OVERFLOW
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LDA :MLEN
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SEC
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SBC :S1LEN
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BCC :EXIT
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; EXIT IF MLEN < S1LEN
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STA :SCNT ; ORIG STR WAS TOO LONG
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LDA :MLEN
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STA :S1LEN ; SET STR1 LENGTH TO MAX
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JMP :DOCAT
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*
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** RESULTING LENGTH DOES NOT EXCEED MAX
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** LENGTH OF STRING 1 = S1LEN + S2LEN
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** INDICATE NO OVERFLOW, __SOVF = 0
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** SET NUM OF CHARS TO CONCAT TO LENGTH OF STR 2
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*
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:LENOK
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STA :S1LEN
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LDA #0 ; SAVE SUM OF 2 LENGTHS
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STA :SOVF ; INDICATE NO OVERFLOW
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LDA :S2LEN
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STA :SCNT ; COUNT = LENGTH OF STRING 2
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*
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** CONCAT STRINGS
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*
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:DOCAT
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LDA :SCNT
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BEQ :EXIT ; EXIT IF NO BYTES LEFT
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*
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:CATLP
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LDY :S2IND
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LDA (ADDR2),Y ; GET NEXT BYTE FROM S2
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LDY :S1IND
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STA (ADDR1),Y ; MOVE IT TO END OF STR 1
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INC :S1IND ;INC STRING 1 INDEX
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INC :S2IND ; INC STRING 2 INDEX
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DEC :SCNT ; DECREMENT COUNTER
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BNE :CATLP ; CONT UNTIL __SCNT = 0
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*
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:EXIT
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*
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** UPDATE STRING1 LENGTH
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*
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LDA :S1LEN
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LDY #0
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STA (ADDR1),Y
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LDA :SOVF
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ROR A
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*
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** RESTORE RETURN ADDRESS
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*
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LDA RETADR+1
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PHA
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LDA RETADR
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PHA
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*
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** COPY TO [RETURN]
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*
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LDY #0
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LDA (ADDR1),Y ; LENGTH OF STRING
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STA RETLEN
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LDA #1
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:RLP
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LDA (ADDR1),Y
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STA RETURN,Y
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CPY RETLEN
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INY
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BNE :RLP
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LDA RETLEN
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LDY #0
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STA (ADDR1),Y
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*
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LDX :S3LEN ; RETURN FINAL LENGTH
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*
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RTS
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*
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** DATA
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*
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:S3LEN DS 1
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:S1LEN DS 1
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:S1IND DS 1
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:S2LEN DS 1
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:S2IND DS 1
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:MLEN DS 1
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:SCNT DS 1
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:SOVF DS 1
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*
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