mirror of https://github.com/RevCurtisP/C02.git
218 lines
7.3 KiB
Plaintext
218 lines
7.3 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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SUBROUTINE STDLIB
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;abs(n) - Get ABSolute Value
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;Args: A = Number to get Absolute Value Of
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;Affects: C, N, Z
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;Returns: A = Absolute Value of Argument
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ABS: CMP #$80 ;If Negative (High Bit Set)
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BCC .ABSX ; Carry will Already be Set
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EOR #$FF ; One's Complement
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ADC #$00 ; and Increment (Carry set by CMP)
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.ABSX RTS
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;max(m,n) - Get MAXimum of Two Numbers
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;Args: A,Y = Numbers to Compare
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;Sets: TEMP0 = Second Argument
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;Affects: N,Z,C
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;Returns: A = Larger of the Two Arguments
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MAX: STY TEMP0 ;Save Second Parameter
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CMP TEMP0 ;If First Parameter
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BCC .MAXX ; Greater than Second Parameter
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TYA ;Copy Second Parameter into Accumulator
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.MAXX RTS
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;min(m,n) - Get MINimum Get MAXimum of Two Numbers
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;Args: A,Y = Numbers to Compare
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;Sets: TEMP0 = Second Argument
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;Affects: N,Z,C
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;Returns: A = Smaller of the Two Arguments
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MIN: STY TEMP0 ;Save Second Parameter
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CMP TEMP0 ;If First Parameter
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BCS .MINX ; Less than Second Parameter
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TYA ;Copy Second Parameter into Accumulator
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.MINX RTS
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;mult(m,n) - MULTiply Two Numbers
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;Args: A = Multiplicand
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; Y = Nultiplier
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;Sets: TEMP0 = Multiplicand
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; TEMP1 = 0
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; TEMP2 = Product MSB
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;Affects: N,Z,C
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;Returns: A = Product LSB
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; Y = Product MSB
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MULT: STA TEMP0 ;Store Multiplicand
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STY TEMP1 ;Store Multiplier
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;Multiply TEMP0 times TEMP1
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MULTT: LDA #$00 ;Initialize Accumulator
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BEQ .MULTE ;Enter Loop
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.MULTA CLC
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ADC TEMP0 ;Add Multiplicand
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.MULTL ASL TEMP0 ;Shift Multiplicand Left
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.MULTE LSR TEMP1 ;Shift Multiplier Right
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BCS .MULTA ;If Bit Shifted Out, Add Multiplicand
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BNE .MULTL ;Loop if Any 1 Bits Left
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LDY TEMP2 ;Load Y with MSB
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TAX ;and Copy LSB to X
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RTS
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;div(m,n) - MULTiply Two Numbers
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;Args: A = Dividend
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; Y = Divisor
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;Sets: TEMP0 = 0
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; TEMP1 = Divisor
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;Affects: N,Z,C
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;Returns: A = Quotient
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; Y = Remainder
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DIV: STA TEMP0 ;Store Dividend
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STY TEMP1 ;Store Divisor
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;Divide TEMP0 by TEMP1
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DIVT: LDA #$00 ;Clear Accumulator
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LDX #$07 ;Load Loop Counter
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CLC
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.DIVL ROL TEMP0 ;Shift Bit Out of Dividend
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ROL ; into Accumulator
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CMP TEMP1 ;If Accumulator
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BCC .DIVS ; >= Divisor
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SBC TEMP1 ;Subtract Divisor
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.DIVS DEX ;Decrement Counter
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BPL .DIVL ; and Loop
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ROL TEMP0 ;Shift Result into Dividend
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TAY ;Copy Remainder to Y Register
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LDA TEMP0 ;Load Result into Accumulator
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RTS
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;Generate Pseudo-Random Number between 1 and 255
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;Uses RANDOM (must be non-zero on entry)
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;Affects A,N,Z,C
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RAND: LDA RANDOM ;Load Last Result
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ASL ;Shift the Seed
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BCC .RANDX ;If a one was shifted out
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EOR #$1D ; Twiddle the bite
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.RANDX STA RANDOM ;Save the Seed
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RTS
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;Seed Pseudo-Random Number Generator
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;Uses RDSEED (if A is zero)
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;Affects A,N,Z,C
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;Sets RANDOM
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RANDS: ORA #$00 ;If Passed Value not 0
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BNE .RANDX ; Store in Seed and Return
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LDA RDSEED ;Load System Generated Seed
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BNE .RANDX ;If Not 0, Store and Return
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ADC #$01 ;Else Add 1 or 2
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BNE .RANDX ; then Store and Return
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;atoc(&s) - ASCII string TO Character
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;Args: Y,X = Address of String to Convert
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;Uses: TEMP0, TEMP1
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;Sets: SRCLO, SRCHI = Address of String
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;Returns: A = Converted Number
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; C,N,Z based on Accumulator
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; Y = Number of Digits
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ATOC: JSR SETSRC ;Initialize Source String
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STY TEMP0 ;Initialize Result
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.ATOCL LDA (SRCLO),Y ;Get Next Character
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CMP #$30 ;If Less Than '0'
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BCC .ATOCX ; Exit
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CMP #$3A ;If Greater Than '9'
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BCS .ATOCX ; Exit
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AND #$0F ;Convert to Binary Nybble
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STA TEMP1 ; and Save It
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LDA TEMP0 ;Load Result
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ASL ;Multiply by 5 by
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ASL ; Multiplying by 4
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ADC TEMP0 ; And Adding Itself
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ASL ;Multiply that by 2
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ADC TEMP1 ;Add Saved Nybble
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STA TEMP0 ; and Store Result
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INY ;Increment Index
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BPL .ATOCL ; and Loop
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.ATOCX LDA TEMP0 ;Load Result
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RTS ;And Return
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;ctoa(n) - Character TO ASCII string
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;Args: Y,X = Address of String to Populate
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;Sets: DSTLO, DSTHI = Address of String
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; TEMP0 = Ones Digit
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; TEMP1 = Tens Digit
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; TEMP2 = Hundreds Digit
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;Affects: C,N.Z
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;Returns: A,Y = Length of String
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CTOA: JSR SETDST ;Initialize Destination String
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LDY #0 ;Initialize Index into String
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JSR CUBCD ;Convert Accumulator to Unpacked BCD
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LDA TEMP2 ;Get MSB
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BEQ .CTOA1 ;If Not Zero
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JSR .CTOAN ; Convert Low Nybble
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.CTOA1 LDA TEMP1 ;Get Low Byte
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BNE .CTOA2 ;If Not Zero
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CMP TEMP2 ; and Hundreds
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BEQ .CTOA3 ; not Zero
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.CTOA2 JSR .CTOAN ; Convert It
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.CTOA3 LDA TEMP0 ;Get Low Byte
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JSR .CTOAN ;and Convert Low Nybble
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LDA #$00
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BEQ .CTOAX ;Terminate String
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.CTOAN ORA #$30 ;Convert to ASCII digit
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.CTOAX STA (DSTLO),Y ;Store in String
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INY ;and Increment Offset
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TYA ;Copy String Length to Accumulator
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RTS
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;cubcd(n) - Convert and Unpack BCD number
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;Args: A - Number to Convert
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;upbcd() - UnPack 3-digit BCD number
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;Uses: TEMP1 = Low Byte
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; TEMP2 = High Nybble
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;Sets: TEMP0 = Ones Digit
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; TEMP1 = Tens Digit
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; TEMP2 = Hundreds Digit
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;Affects: A,N,Z
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;Returns: X = 0
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CUBCD: JSR CVBCD ;Convert Accumulator to BCD
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UPBCD: LDA TEMP1 ;Get Low Byte
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AND #$0F ;Strip High Nybbleet
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STA TEMP0 ;Save in Ones
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LDA TEMP1 ;Get Low Byte
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LSR ;Shift High Nybble
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LSR ; into Low Nybble
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LSR
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LSR
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STA TEMP1 ;Save in Tens
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RTS
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;ConVert number to packed Binary Coded Decimal
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;Args: A - Number to Convert
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;Destroys: TEMP0
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;Sets: TEMP1 = Tens and Ones Digit
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; TEMP2 = Hundreds Digit
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;Returns: A = Hundreds Digit
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; X = 0
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CVBCD: STA TEMP0 ;Save Binary Value
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CVBCDT: LDA #0 ;Clear BCD Bytes
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STA TEMP1
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STA TEMP2
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LDX #8 ;Process 8 bits of Binary
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PHP ;Save Status Register
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SEI ;Disable Interupts
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SED ;Set Decimal Mode
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.CVBCDL ASL TEMP0 ;Shift High Bit into Carry
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LDA TEMP1 ;Add BCD Low Byte to Itself
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ADC TEMP1 ; Plus Bit Shifted out of Binary
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STA TEMP1 ; Effectively Multiplying It by 2
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LDA TEMP2 ;Add BCD MSB to Itself
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ADC TEMP2 ; Plus Bit Shifted out of Low Byte
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STA TEMP2 ; Effectively Multiplying It by 2
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DEX ;Decrement Counter and
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BNE .CVBCDL ; Process Next Bit
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PLP ;Restore Status Register
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RTS
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ENDSUBROUTINE
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