mirror of
https://github.com/nathanriggs/AppleIIAsm-Collection.git
synced 2024-12-03 18:49:28 +00:00
197 lines
4.5 KiB
Plaintext
197 lines
4.5 KiB
Plaintext
*
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*``````````````````````````````*
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* NUM2STR :: NUMBER TO STRING *
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*- -*
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* CONVERTS A 16-BIT NUMBER TO *
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* ITS STRING EQUIVALENT. *
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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 #>11111 ; VALUE TO *
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* PHA ; CONVERT *
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* LDA #<11111 *
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* PHA *
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* JSR NUM2STR *
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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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* LO BYTE VALUE TO CONVERT *
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* HI BYTE VALUE TO CONVERT *
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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 = COUNTER; TRASH *
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* .X = COUNTER; TRASH *
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* .A = LOW BYTE OF RET ADDR *
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* *
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* [RETURN] = STRING VALUE *
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* [RETLEN] = LENGTH OF STRING *
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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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NUM2STR
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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 :VALSTR
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PLA
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STA :VALSTR+1
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*
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STA :NGFLAG
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BPL :GETBP ; BR IF VAL IS POS
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LDA #0
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SEC
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SBC :VALSTR
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STA :VALSTR
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LDA #0
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SBC :VALSTR+1
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STA :VALSTR+1
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*
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:GETBP
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LDA #<RETURN
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STA ADDR1 ; ADDRESS TO STORE STRING
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LDA #>RETURN+1
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STA ADDR1+1
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LDA #0 ; SET BUFFER TO EMPTY
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LDY #0
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STA (ADDR1),Y ; BUFFER(0) = 0
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*
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** CONVERT VAL TO STRING
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*
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:CNVERT
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*
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** VALUE = VALUE DIV 10
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** MOD10 = VALUE MOD 10
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*
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LDA #0
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STA :MOD10
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STA :MOD10+1
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LDX #16
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CLC ; CLEAR CARRY
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*
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:DVLOOP
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ROL :VALSTR ; SHIFT CARRY INTO DIVBIT 0
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ROL :VALSTR+1 ; WHICH WILL BE THE QUOTIENT
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ROL :MOD10 ; + SHIFT DIV AT SAME TIME
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ROL :MOD10+1
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*
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** A,Y = DIVIDEND - DIVISOR
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*
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SEC
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LDA :MOD10
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SBC #10
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TAY ; SAVE LOWB IN REG Y
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LDA :MOD10+1
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SBC #0 ; SUBTRACT CARRY
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BCC :DECCNT ; BR IF DEND < DIVISOR
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STY :MOD10 ; ELSE
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STA :MOD10+1 ; NXT BIT OF Q IS A ONE AND SET
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; DIVIDEND = DEND - DIVISOR
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:DECCNT
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DEX
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BNE :DVLOOP
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ROL :VALSTR ; SHIFT IN LAST CARRY FOR Q
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ROL :VALSTR+1
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*
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** CONCAT NEXT CHAR
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*
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:CONCH
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LDA :MOD10
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CLC
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ADC #$B0
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*
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** ADC #'0' ; CONVERT 0..9 TO ASCII 0-9
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*
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JSR :CONCAT
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*
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** IF VALUE <> 0 THEN CONTINUE
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*
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LDA :VALSTR
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ORA :VALSTR+1
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BNE :CNVERT ; BR IF VALUE != 0
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*
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:EXIT
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LDA :NGFLAG
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BPL :POS ; BR IF ORIG VAL POS
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LDA #173 ; ELSE
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JSR :CONCAT ; PUT A MINUS SIGN IN FRONT
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*
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:POS
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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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RTS ; RETURN
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*
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********************************
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* CONCAT SUBROUTINE
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********************************
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*
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:CONCAT
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PHA ; SAVE CHAR ON STACK
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*
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** MOVE BUFFER RIGHT ONE CHAR
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*
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LDY #0
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LDA (ADDR1),Y ; GET CURRENT LENGTH
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TAY
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BEQ :EXITMR ; BR IF LENGTH=0
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*
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:MVELP
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LDA (ADDR1),Y ; GET NEXT CHAR
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INY
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STA (ADDR1),Y ; STORE IT
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DEY
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DEY
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BNE :MVELP ; CONT UNTIL DONE
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*
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:EXITMR
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PLA ; GET CHAR BACK FROM STACK
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LDY #1
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STA (ADDR1),Y ; STORE THE CHAR
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LDY #0
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LDA (ADDR1),Y ; GET LENGTH BYTE
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CLC
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ADC #1 ; INC LENGTH BY ONE
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STA (ADDR1),Y ; UPDATE 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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:NGFLAG DS 1
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:VALSTR DS 2
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:MOD10 DS 2
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*
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