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303 lines
10 KiB
Plaintext
303 lines
10 KiB
Plaintext
; C02 library stdlib.h02 assembly language subroutines
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; Requires
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; external zero page locations SRCLO and SRCHI
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; and external locations RANDOM, RDSEED, TEMP0, TEMP1, and TEMP2.
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;iabs(n) - Get Integer ABSolute Value
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;Args: Y,X = Integer to get Absolute Value Of
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;Sets: TEMP1, TEMP2
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;Affects: C, N, Z
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;Returns: A = Absolute Value of Argument
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IABS: CPY #$80 ;If Negative (High Bit Set)
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BCC IABSX ; Carry will Already be Set
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JSR SAVRXY ; Copy LSB, MSB to TEMP1. TEMP2
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LDA #0 ; Subtract LSB
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SBC TEMP1 ; from 0
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TAX ; and Copy to X Register
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LDA #0 ; Subtract MSB
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SBC TEMP2 ; from 0
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TAY ; and Copy to Y Register
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IABSX: RTS
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;imax(i) - Get MAXimum of Two Integers
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;Args: Y,X = Second Integer
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;Uses: SRCHI,SRCLO = First Integer
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;Affects: N,Z,C
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;Returns: Y,X = Larger of the Two Arguments
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IMAX: CPY SRCHI ;If Y < SRCHI
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BCC IMAXC ; Return SRCLO, SRCHI
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CPX SRCLO ;IF X >= SRCLO
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BCS IMINX ; Return Argument
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IMAXC: JMP GETSRC ;Return Integer in SRCLO, SRCHI
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;imin(i) - Get MINimum of Two Integers
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;Args: Y,X = Second Integer
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;Uses: SRCHI,SRCLO = First Integer
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;Affects: N,Z,C
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;Returns: Y,X = Larger of the Two Arguments
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IMIN: CPY SRCHI ;If Y < SRCHI
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BCC IMINX ; Return Argument
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BNE IMAXC ;If Y > SRCHI Return SRCHI,SRCLO
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CPX SRCLO ;If X >= SRCLO
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BCS IMAXC ; Return SRCHI,SRCLO
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IMINX: RTS ;Return Argument
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;iaddc(c,i) - Add Byte c to Integer i
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IADDC: JSR SETSRC ;Save Integer and Clear Y
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TAX ;Copy Byte to LSB and drop into IADD
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;iadd(d) - ADD Integer d to from Integer g
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;Args: Y,X = Addend
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;Requires: setsrc(g) - Augend
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;Sets: TEMP1,TEMP2 = Addend
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;Affects: Z,C
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;Returns: A = Sum (Bits 16-23)
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; Y,X = Sum (Bits 0-15)
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; N = Sign of Result
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IADD: CLC ;Clear Carry for Addition
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TXA ;Add Addend LSB
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ADC SRCLO ;to Augend LSB
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TAX ;and Copy to X
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TYA ;Add Addend MSB
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ADC SRCHI ;to Augebd MSB
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TAY ;and Copy to Y
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LDA #0 ;Set Overflow to 0
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ROL ; Rotate Carry (Same as Adding it)
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RTS ; and Return
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;isub(s) - SUBtract Integer s from Integer m
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;Args: Y,X = Subtrahend
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;Requires: setsrc(m) - Minuend
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;Sets: TEMP1,TEMP2 = Subtrahend
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;Affects: Z,C
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;Returns: A = Differencee (Bits 16-23)
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; Y,X = Difference (Bits 0-15)
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; N = Sign of Result
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ISUB: JSR SAVRXY ;Store Subtrahend in TEMP1,TEMP2
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SEC ;Set Carry for Subtraction
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LDA SRCLO ;Load Minuend LSB
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SBC TEMP1 ;Subtract Subtrahend LSB
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TAX ;Copy Difference LSB to X
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LDA SRCHI ;Load Minuend MSB
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SBC TEMP2 ;Subtract Subtrahend MSB
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TAY ;Copy Difference MSB to Y
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LDA #0 ;Set Overflow Byte to 0
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SBC #0 ; Subtract Carry
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RTS ; and Return
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;imult(m) - MULTiply Two Integers
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;Args: Y,X - Multiplier
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;Requires: DSTHI,DSTLO = Multiplicand
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;Sets: TEMP0-TEMP3 = 32 Bit Product
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;Destroys: SRCHI, SRCLO
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;Affects: A,C,Z,N
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;Returns: Y,X = 16 Bit Product
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IMULT: JSR SETSRC ;Save Multiplier
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STY TEMP2 ;Clear Upper Bits of Product
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STY TEMP3
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LDX #16 ;Rotate Through 16 Bits
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IMULTS: LSR SRCHI ;Divide Multiplier by 2
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ROR SRCLO
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BCC IMULTR ;If Shifted out Bit is 1
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LDA TEMP2 ; Add Multiplicand
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CLC ; to Upper Half of Product
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ADC DSTLO
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STA TEMP2
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LDA TEMP3
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ADC DSTHI
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IMULTR: ROR ;Rotate Partial Product
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STA TEMP3
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ROR TEMP2
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ROR TEMP1
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ROR TEMP0
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DEX ;Decrement Counter
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BNE IMULTS ;and Process Next Bit
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LDX TEMP0
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LDY TEMP1 ;Return Low 16 Bits of Product
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RTS
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;idiv(d) - DIVide Two Numbers
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;Args: Y,X - Divisor
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;Requires: DSTHI,DSTLO = Dividend
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;Sets: SRCHI,SRCLO = Divisor
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; DSTHI,DSTLO = Quotient
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; TEMP1,TEMP2 = Remainder
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;Affects: A,C,Z,N
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;Returns: Y,X = 16 Bit Quotient
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IDIV: JSR SETSRC ;Save Divisor
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STA TEMP1
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STA TEMP2
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LDX #16 ;repeat for each bit: ...
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IDIVL: ASL DSTLO ;dividend lb & hb*2, msb -> Carry
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ROL DSTHI
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ROL TEMP1 ;remainder lb & hb * 2 + msb from carry
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ROL TEMP2
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LDA TEMP1
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SEC
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SBC SRCLO ;substract divisor to see if it fits in
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TAY ;lb result -> Y, for we may need it later
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LDA TEMP2
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SBC SRCHI
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BCC IDIVS ;if carry=0 then divisor didn't fit in yet
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STA TEMP2 ;else save substraction result as new remainder,
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STY TEMP1
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INC DSTLO ;and INCrement result cause divisor fit in 1 times
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IDIVS: DEX
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BNE IDIVL
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RTS
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;ishftl(n,i) - Shift Integer i to the Left n Bits
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;Sets: TEMP1, TEMP2 = LSB, MSB of Result
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;Affects: A,Y,N,Z,C
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;Returns: Y,X = Shifted Integer
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ISHFTL: JSR SAVRXY ;Save X,Y in TEMP1,TEMP2
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TAY ;Set Counter to Number of Bits
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ASL TEMP1 ;Shift LSB to Left
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ROL TEMP2 ;Rotate MSB to Left
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DEY ;Decrement Counter
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BNE ISHFTL ; and Loop if Not 0
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BEQ ISHFTX ;Return Shifted Integer
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;ishftr(n,i) - Shift Integer i to the Right n Bits
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;Sets: TEMP1, TEMP2 = LSB, MSB of Result
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;Affects: A,Y,N,Z,C
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;Returns: Y,X = Shifted Integer
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ISHFTR: JSR SAVRXY ;Save X,Y in TEMP1,TEMP2
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TAY ;Copy
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LSR TEMP1 ;Shift LSB to Right
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ROR TEMP2 ;Rotate MSB to Right
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DEY ;Decrement Counter
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BNE ISHFTR ; and Loop if Not 0
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ISHFTX: JMP RESRXY ;Load Shifted Integer and Return
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;atoi(&s) - ASCII string TO Integer
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;Args: Y,X = Address of String to Convert
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;Sets: TEMP1, TEMP2 = Integer Value
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;Affects: TEMP0
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;Returns: A = Number of Digits
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; Y,X = Integer Value
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ATOI: JSR SETSRC ;Initialize Source String
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STY TEMP1 ;Initialize Result
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STY TEMP2
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ATOIL: LDA (SRCLO),Y ;Get Next Character
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CMP #$30 ;If Less Than '0'
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BCC ATOIX ; Exit
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CMP #$3A ;If Greater Than '9'
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BCS ATOIX ; Exit
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AND #$0F ;Convert to Binary Nybble
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STA TEMP0 ; and Save It
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LDA TEMP1 ;Load Result
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LDX TEMP2
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ASL TEMP1 ;Multiply by 5 by
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ROL TEMP2
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ASL TEMP1 ; Multiplying by 4
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ROL TEMP2
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CLC ; And Adding Itself
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ADC TEMP1
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STA TEMP1
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TXA
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ADC TEMP2
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STA TEMP2
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ASL TEMP1 ;Multiply that by 2
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ROL TEMP2
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LDA TEMP0 ;Get Saved Nybble
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CLC ;and Add to Result
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ADC TEMP1 ;Add Saved Nybble
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STA TEMP1 ; and Store Result
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LDA #0
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ADC TEMP2
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STA TEMP2
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INY ;Increment Index
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BPL ATOIL ; and Loop
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ATOIX: TYA ;Return Number of Digits
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JMP RESRXY ;and Integer Value
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;itoa(n) - Integer TO ASCII string
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;Args: Y,X = Integer Value to Convert
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;Uses: DSTHI,DSTLO = Destination String
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;Returns: A,Y = Length of String
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ITOA: JSR CVIBCD ;Convert Integer to Packed BCD
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LDY #0 ;Initialize Index into String
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STY TEMP3
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ITOAA: LDY #4 ;Set Initial Digit Number
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ITOAZ: JSR UPBCDI ;Unpack Digit Y
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BNE ITOAS ;If Zero
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DEY ; Decrement Digit Number
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BNE ITOAZ ; If Not Zero Loop
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BEQ ITOAS ; Else IDIVS Unpack
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ITOAL: JSR UPBCDI ;Unpack Digit #Y
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ITOAS: TAX ;Save Digit in X
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TYA ;Push Digit Number into Stack
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PHA
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TXA ;and Restore Digit
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LDY TEMP3 ;Get Index into String
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ORA #$30 ;Convert Digit to ASCII
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STA (DSTLO),Y ;and Store in String
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INC TEMP3 ;Increment Index into String
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PLA ;Pull Digit Number off Stack
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TAY
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DEY ;Decrement Digit Number
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BPL ITOAL ;Loop if >= Zero
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LDA #0 ;Terminate String
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STA (DSTLO),Y
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TYA ;Return String Length
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RTS
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;upbcdi() - UnPack digits from BCD Integer
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; Assumes that TEMP0, TEMP1, and TEMP2
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; are in consecutive memory locations
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;Args: Y = Digit Number to Unpack (0-5)
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;Uses: TEMP0 = Low Byte
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; TEMP1 = Middle Byte
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; TEMP2 = High Nybble
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;Affects: X,C,N,Z
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;Returns: A = Unpacked Digit
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UPBCDI: TYA ;Divide Digit Number by 2,
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LSR ; Setting Carry
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TAX ; if Digit Number is Odd
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LDA TEMP0,X ;Load BCD Byte
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BCC UPBCDS ;If Digit Number is Odd
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LSR ;Shift High Nybble to Low Nybble
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LSR
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LSR
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LSR
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UPBCDS: AND #$0F ;Strip Off High Nybble
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RTS
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;cvibcd(int) - ConVert Integer to packed Binary Coded Decimal
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;Args: Y,X - Integer to Convert
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;Sets: TEMP0 = Tens and Ones Digit
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; TEMP1 = Thousands and Hundreds Digit
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; TEMP2 = Ten-Thousands Digit
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;Affects: A,X,Y
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CVIBCD: LDA #0 ;Clear BCD Bytes
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STA TEMP0
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STA TEMP1
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STA TEMP2
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PHP ;Save Status Register
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SEI ;Disable Interrupts
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SED ;Set Decimal Mode
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TYA ;Push MSB onto Stack
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PHA
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TXA ;Push LSB onto Stack
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PHA
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TSX ;Copy Stack Pointer to X
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LDY #16 ;Process 16 bits of Binary
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CVIBCL: ASL $101,X ;Shift High Bit Into Carry
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ROL $102,X
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LDA TEMP0 ;Add 6 Digit BCD Number Itself
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ADC TEMP0 ; Effectively Multiplying It by 2
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STA TEMP0 ; and Adding in the Shifted Out Bit
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LDA TEMP1
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ADC TEMP1
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STA TEMP1
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LDA TEMP2
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ADC TEMP2
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STA TEMP2
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DEY ;Decrement Counter and
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BNE CVIBCL ; Process Next Bit
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PLA ;Restore Stack
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PLA
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PLP ;Restore Status Register
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RTS
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