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205 lines
6.9 KiB
Plaintext
205 lines
6.9 KiB
Plaintext
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;*** Needs to be Tested and Debugged ****
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;C02 library stack.h02 assembly language subroutines
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;Requires External Zero Page Variables
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;STKLO, STKHI, DSTLO, DSTHI, SRCLO, SRCHI
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;External Variables
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;STKSLO, STKSHI, STKELO, STKEHI, STKLEN, TEMP0, TEMP1, TEMP2
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;External Routines
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;MEMCPL, SETDST, SETSRC, STRLEN
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;Implementation Notes:
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;Stack starts at STKSLO,STKSHI and builds upward tp STKELO, STKEHI
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;Each entry on the stack consists of the entry data followed
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;by a single byte containing the length of the entry data
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;stkbgn(&b) - Set Stack Start Address
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;Args: X,Y = Address
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;Sets: STKSLO, STKSHI = Stack Start Address
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;Affects: Z, N
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STKBGN: STX STKSLO ;Save Stack Start LSB
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STY STKSHI ;Save Stack Start MSB
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RTS
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;stkend(&b) - Set Stack End Address (+1)
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;Args: X,Y = Address
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;Sets: STKELO, STKEHI = Stack End Address
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;Affects: Z, N
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STKEND: STX STKELO ;Save Stack End LSB
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STY STKEHI ;Save Stack End MSB
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RTS
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;STKPTR() - Get Stack Pointer
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;Uses: STKLO,STKHI = Stack Pointer
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;Affects: X,N,Z
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;Returns: X = Stack Pointer LSB
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; Y = Stack Pointer MSB
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STKPTR: LDX STKLO ;Load Stack Pointer LSB
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LDY STKHI ;Load Stack Pointer MSB
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RTS
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;STKSRC() - Set Source Pointer to Stack Pointer
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;Uses: STKLO,STKHI = Stack Pointer
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;Sets: SRCLO,SRCHI = Source Array Pointer
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;Affects: X,N,Z
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;Returns: Y = 0
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STKSRC: JSR STKPTR ;Get Stack Pointer Address
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JMP SETSRC ;Set Source/ an/d Return
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;stkdst() - Set Destination Pointer to Stack Pointer
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;Uses: STKLO,STKHI = Stack Pointer
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;Sets: DSTLO,DSTHI = Destination Array Pointer
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;Affects: N,Z
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;Returns: X = Stack Pointer LSB
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; Y = Stack Pointer MSB
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STKDST: JSR STKPTR ;Get Stack Pointer Address
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JMP SETDST ;Set Destination and Return
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;stkrst() - Reset Stack Pointer to Start Address
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;Uses: STKSLO, STKSHI = Stack Start Address
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;Sets: STKLO, STKHI = Stack Pointer
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;Affects: Z, N
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;Returns: X = Stack Pointer LSB
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; Y = Stack Pointer MSB
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STKRST: LDX STKSLO ;Load X with Stack Start LSB
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LDY STKSHI ;Load X with Stack Start MSB
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;stkset() - Set Stack Pointer Address
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;Args: X,Y = Address
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;Sets: STKLO, STKHI = Stack Pointer Address
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;Affects: Z, N
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;Returns: X = Stack Pointer LSB
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; Y = Stack Pointer MSB
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STKSET: STX STKLO ;Store X in Stack Pointer LSB
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STY STKHI ;Store Y in Stack Pointer MSB
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RTS ;Exit Routine
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;stkalc(n) - Allocate Space on Stack
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;Args: A=Number of Bytes to Allocate
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;Updates: STKLO, STKHI = Stack Pointer
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;Affects: C,N,Z
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;Returns: A = Number of Bytes Allocated
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; 0 if Error: Pointer Overflow or Length 0
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; Y=0
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STKALC: LDA TEMP0 ;If No Bytes
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BEQ STKINX ; Return False
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CLC
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ADC STKLO ;Add to Stack Pointer LSB
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STA STKLO ;and Save
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LDA STKHI ;Add Carry
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ADC #0 ;to Stack Pointer MSB
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STA STKHI ;and Save
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LDA STKEHI ;If Stack End MSB
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CMP STKHI ; < Stack Pointer MSB
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BCC STKSUZ ; Return False
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BNE STKALX ;Else if Not Equal
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LDA STKELO ;and Stack End LSB
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CMP STKLO ; < Stack Pointer LSB
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BCC STKSUZ ; Return False
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STKALX: LDA TEMP0 ;Get Number of Bytes from X Register
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LDY #0 ;Initialize Index
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STA (STKLO),Y ;Store after Allocated Area
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;and fall inro STKINC
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;stkinc(n) - Increment Stack Pointer
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;Sets: STKLO, STKHI = Stack Pointer Address
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;Affects: Y,Z,N
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STKINC: INC STKLO ;Increment LSB
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BNE STKINX ;If Zero
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INC STKHI ; Increment MSB
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STKINX: RTS
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;stkpsh(n, &m) - Push n Bytes of m onto Stack
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;Args: A = Number of Bytes to Append
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; Y,X = Address of Source Array
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;Uses: STKELO, STKEHI = Stack End Address
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;Sets: DSTLO, DSTHI = Pointer to Stack Entry
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; SRCHI, SRCLO = Pointer to Source Array
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; TEMP0 = Number of Bytes to Append
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;Updates: STKLO, STKHI = Stack Pointer
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;Returns: A=Number of Bytes Pushed
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; 0 = Error: Stack Underflow
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STKPSH: JSR SETSRC ;Set Source Address
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STKPSA: STA TEMP0 ;Save Number of Bytes
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JSR STKDST ;Set Destination to Stack Pointer
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JSR STKALC ;Allocate Space on Stack
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BEQ STKDER ;If Error Return FALSE
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JMP MEMCPL ;Else Copy Bytes and Return
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;stkcmp - Compare Stack Pointer to Stack Start Address
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;Uses: STKLO, STKHI = Stack Pointer Address
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; STKSLO, STKSHI = Stack Start Address
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;Returns: C=1,Z=1 if Stack Pointer = Stack Start
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; C=1,Z=0 if Stack Pointer > Stack Start
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; C=0,Z=0 if Stack Pointer < Stack Start
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STKCMP: LDA STKHI ;Compare MSB
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CMP STKSHI
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BCC STKCMX ;If Pointer<Start Return C=0, Z=1
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BNE STKCMX ;If Pointer>Start Return C=1. Z=0
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LDA STKLO ;If MSB Equal
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CMP STKSLO ;Compare LSB
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STKCMX: RTS
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;stkdec(n) - Decrement Stack Pointer
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;Sets: STKLO, STKHI = Stack Pointer Address
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;Affects: X,Z,N
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STKDEC: LDX STKLO ;If LSB
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BNE STKDEL ; is Zero
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DEC STKHI ; Decrement MSB
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STKDEL: DEC STKLO ; Decrement LSB
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STKDER: RTS
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;stkdal() - Deallocate Stack Entry
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;Uses: STKSLO, STKSHI = Stack Start Address
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;Updates: STKLO, STKHI = Stack Pointer
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;Affects: C,N,Z
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;Returns: A = Number of Bytes in Entry
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; 0 = Error: Stack Underflow
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; Y = 0
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STKDAL: LDY #0 ;Initialize Index
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JSR STKCMP ;If Stack Pointer
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BCC STKSUZ ; <= Stack Start
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BEQ STKSUZ ; Return 0
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JSR STKDEC ;Decrement Stack Pointer
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LDA (STKLO),Y ;Get Number of Bytes in Entry
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;and fall into STKSUB
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;stksub(n) - Reduce Stack Pointer by A
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STKSUB: STA TEMP0 ;Save Number in TEMP0
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LDA STKLO
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SEC ;Subtract A from LSB
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SBC TEMP0
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STA STKLO
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LDA STKHI ;Subtract 0 from LSB
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SBC #0 ;For Borrow
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STA STKHI
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STKSUC: JSR STKCMP ;If Stack Pointer LSB
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BCC STKSUE ; < Stack Pointer
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STKSUE: LDA TEMP0 ;Retrieve Number of Bytes
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RTS
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STKSUZ: LDA #0 ;Set A to 0
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RTS
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;stkpop(&m) - Pop Top Entry off Stack
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;Args: Y,X = Address of Source Array
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;Uses: STKSLO, STKSHI = Stack Start Address
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;Updates: STKLO, STKHI = Stack Pointer
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;Affects: C,N,Z
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;Returns: A,Y = Number of Bytes in Entry
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; 0 = Error: Stack Underflow
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STKPOP: JSR SETDST ;Set Destination Address
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JSR STKDAL ;Deallocate Stack Entry
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BEQ STKDER ;If Underflow, Return 0
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JSR STKSRC ;Set Source Address to Stack Pointer
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JMP MEMCPL ;Copy Bytes and Return
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;stkstr(n, &m) - Push String onto Stack
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;Args: Y,X = Address of Source Array
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STKSTR: JSR STRLEN ;Get Length of String
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BEQ STKSTY ;If Length > 0
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BMI STKSTY ; and < 128
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INY ; Increment Length to
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TYA ; include null terminator
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STKSTY: LDY #0 ;Clear Y Index
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BEQ STKPSA ;Execute STKPSH, skippping SETSRC
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