mirror of
https://github.com/RevCurtisP/C02.git
synced 2024-10-31 10:14:09 +00:00
245 lines
8.2 KiB
Plaintext
245 lines
8.2 KiB
Plaintext
;C02 stack module assembly language subroutines
|
|
;Requires external zero page variables
|
|
;STKLO, STKHI, DSTLO, DSTHI, SRCLO, SRCHI
|
|
;external variables
|
|
;STKSLO, STKSHI, STKELO, STKEHI, TEMP0, TEMP1, TEMP2
|
|
;external routines
|
|
;MEMCPL, SETDST, SETSRC
|
|
|
|
;Implementation Notes:
|
|
;Stack starts at STKSLO,STKSHI and builds upward tp STKELO, STKEHI
|
|
;Each entry on the stack consists of the entry data followed
|
|
;by a single byte containing the length of the entry data
|
|
|
|
;stkbgn(&b) - Set Stack Start Address
|
|
;Args: X,Y = Address
|
|
;Sets: STKSLO, STKSHI = Stack Start Address
|
|
;Affects: Z, N
|
|
STKBGN: STX STKSLO ;Save Stack Start LSB
|
|
STY STKSHI ;Save Stack Start MSB
|
|
RTS
|
|
|
|
;stkend(&b) - Set Stack End Address (+1)
|
|
;Args: X,Y = Address
|
|
;Sets: STKELO, STKEHI = Stack End Address
|
|
;Affects: Z, N
|
|
STKEND: STX STKELO ;Save Stack End LSB
|
|
STY STKEHI ;Save Stack End MSB
|
|
RTS
|
|
|
|
;stkptr() - Get Stack Pointer
|
|
;Uses: STKLO,STKHI = Stack Pointer
|
|
;Affects: N,Z
|
|
;Returns: X = Stack Pointer LSB
|
|
; Y = Stack Pointer MSB
|
|
STKPTR: LDX STKLO ;Load Stack Pointer LSB
|
|
LDY STKHI ;Load Stack Pointer MSB
|
|
RTS
|
|
|
|
;stkssp() - Save Stack Pointer
|
|
;Uses: STKLO,STKHI = Stack Pointer
|
|
;Sets: TEMP1.TEMP2 = Stack Pointer
|
|
;Affects: N,Z
|
|
;Returns: X = Stack Pointer LSB
|
|
; Y = Stack Pointer MSB
|
|
STKSSP: JSR STKPTR ;Get Stack Pointer
|
|
JMP SAVRXY ;Save in TEMP1, TEMP2
|
|
|
|
;stksrc() - Set Source Pointer to Stack Pointer
|
|
;Uses: STKLO,STKHI = Stack Pointer
|
|
;Sets: SRCLO,SRCHI = Source Array Pointer
|
|
;Affects: X,N,Z
|
|
;Returns: Y = 0
|
|
STKSRC: JSR STKPTR ;Get Stack Pointer Address
|
|
JMP SETSRC ;Set Source/ an/d Return
|
|
|
|
;stkdst() - Set Destination Pointer to Stack Pointer
|
|
;Uses: STKLO,STKHI = Stack Pointer
|
|
;Sets: DSTLO,DSTHI = Destination Array Pointer
|
|
;Affects: N,Z
|
|
;Returns: X = Stack Pointer LSB
|
|
; Y = Stack Pointer MSB
|
|
STKDST: JSR STKPTR ;Get Stack Pointer Address
|
|
JMP SETDST ;Set Destination and Return
|
|
|
|
;stkrst() - Reset Stack Pointer to Start Address
|
|
;Uses: STKSLO, STKSHI = Stack Start Address
|
|
;Sets: STKLO, STKHI = Stack Pointer
|
|
;Affects: Z, N
|
|
;Returns: X = Stack Pointer LSB
|
|
; Y = Stack Pointer MSB
|
|
STKRST: LDX STKSLO ;Load X with Stack Start LSB
|
|
LDY STKSHI ;Load X with Stack Start MSB
|
|
JMP STKSET ;Store in Stack Pointer
|
|
|
|
;stkrsp() - Restore Stack Pointer
|
|
;Uses: TEMP1.TEMP2 = Stack Pointer
|
|
;Sets: STKLO,STKHI = Stack Pointer
|
|
;Affects: N,Z
|
|
;Returns: X = Stack Pointer LSB
|
|
; Y = Stack Pointer MSB
|
|
STKRSP: JSR RESRXY ;Get TEMP1, TEMP2
|
|
;and fall into STKSET
|
|
|
|
;stkset() - Set Stack Pointer Address
|
|
;Args: X,Y = Address
|
|
;Sets: STKLO, STKHI = Stack Pointer Address
|
|
;Affects: Z, N
|
|
;Returns: X = Stack Pointer LSB
|
|
; Y = Stack Pointer MSB
|
|
STKSET: STX STKLO ;Store X in Stack Pointer LSB
|
|
STY STKHI ;Store Y in Stack Pointer MSB
|
|
RTS ;Exit Routine
|
|
|
|
;stkpsh(n, &m) - Push n Bytes of m onto Stack
|
|
;Args: A = Number of Bytes to Append
|
|
; Y,X = Address of Source Array
|
|
;Uses: STKELO, STKEHI = Stack End Address
|
|
;Sets: DSTLO, DSTHI = Pointer to Stack Entry
|
|
; SRCHI, SRCLO = Pointer to Source Array
|
|
; TEMP0 = Number of Bytes to Append
|
|
;Updates: STKLO, STKHI = Stack Pointer
|
|
;Returns: A=Number of Bytes Pushed
|
|
; 0 = Error: Stack Underflow
|
|
STKPSH: JSR SETSRC ;Set Source Address
|
|
STKPSA: STA TEMP0 ;Save Number of Bytes
|
|
JSR STKDST ;Set Destination to Stack Pointer
|
|
JSR STKALC ;Allocate Space on Stack
|
|
JMP MEMCPL ;Copy Bytes and Return
|
|
|
|
;stkadd(n) - Add N Bytes to Stack Pointer
|
|
;Args: A=Number of Bytes to Allocate
|
|
;Updates: STKLO, STKHI = Stack Pointer
|
|
;Affects: A,C,N,Z
|
|
STKADD: CLC
|
|
STKADC: ADC STKLO ;Add to Stack Pointer LSB
|
|
STA STKLO ;and Save
|
|
LDA STKHI ;Add Carry
|
|
ADC #0 ;to Stack Pointer MSB
|
|
STA STKHI ;and Save
|
|
RTS
|
|
|
|
;stkalc(n) - Allocate Space on Stack
|
|
;Args: A=Number of Bytes to Allocate
|
|
;Updates: STKLO, STKHI = Stack Pointer
|
|
;Affects: C,N,Z
|
|
;Returns: A = Number of Bytes Allocated
|
|
; 0 if Error: Pointer Overflow or Length 0
|
|
; Y=0
|
|
STKALC: JSR STKSSP ;Save Stack Pointer
|
|
LDA TEMP0 ;If No Bytes
|
|
BEQ STKABT ; Abort Calling Routine
|
|
JSR STKADD ;Add to Stack Pointer
|
|
LDA STKEHI ;If Stack End MSB
|
|
CMP STKHI ; < Stack Pointer MSB
|
|
BCC STKRPA ; Abort Calling Routine
|
|
BNE STKALX ;Else if Not Equal
|
|
LDA STKELO ;and Stack End LSB
|
|
CMP STKLO ; < Stack Pointer LSB
|
|
BCC STKRPA ; Abort Calling Routine
|
|
STKALX: LDA TEMP0 ;Get Number of Bytes from X Register
|
|
LDY #0 ;Initialize Index
|
|
STA (STKLO),Y ;Store after Allocated Area
|
|
;and fall inro STKINC
|
|
|
|
;stkinc(n) - Increment Stack Pointer
|
|
;Sets: STKLO, STKHI = Stack Pointer Address
|
|
;Affects: Y,Z,N
|
|
STKINC: INC STKLO ;Increment LSB
|
|
BNE STKINX ;If Zero
|
|
INC STKHI ; Increment MSB
|
|
STKINX: RTS
|
|
|
|
;stkcmp - Compare Stack Pointer to Stack Start Address
|
|
;Uses: STKLO, STKHI = Stack Pointer Address
|
|
; STKSLO, STKSHI = Stack Start Address
|
|
;Returns: C=1,Z=1 if Stack Pointer = Stack Start
|
|
; C=1,Z=0 if Stack Pointer > Stack Start
|
|
; C=0,Z=0 if Stack Pointer < Stack Start
|
|
STKCMP: LDA STKHI ;Compare MSB
|
|
CMP STKSHI
|
|
BCC STKRTS ;If Pointer<Start Return C=0, Z=1
|
|
BNE STKRTS ;If Pointer>Start Return C=1. Z=0
|
|
LDA STKLO ;If MSB Equal
|
|
CMP STKSLO ;Compare LSB
|
|
STKRTS: RTS
|
|
|
|
;stkdec(n) - Decrement Stack Pointer
|
|
;Sets: STKLO, STKHI = Stack Pointer Address
|
|
;Affects: X,Z,N
|
|
STKDEC: LDX STKLO ;If LSB
|
|
BNE STKDEL ; is Zero
|
|
DEC STKHI ; Decrement MSB
|
|
STKDEL: DEC STKLO ; Decrement LSB
|
|
STKDER: RTS
|
|
|
|
;stksiz() - Get Stack Size in Bytes
|
|
;Uses: STKLO,STKHI = Stack Pointer
|
|
;Sets: STKSLO, STKSHI = Stack Start Address
|
|
;Returns: A = $FF if Stack Size is Non-Zero
|
|
; $00 if Stack is Empty
|
|
; Y,X = Stack Size (MSB, LSB)
|
|
STKSIZ: LDA STKLO ;Subtract
|
|
SEC ;Start Address LSB
|
|
SBC STKSLO ;from Pointer LSB
|
|
TAX ;and Copy to X
|
|
LDA STKHI ;Subtract Start MSB
|
|
SBC STKSHI ;from Pointer MSB
|
|
TAY ;and Copy to Y
|
|
BCC STKZRO ;Return FALSE if <=0
|
|
BNE STKTRU ;Return TRUE if MSB <> 0
|
|
TXA ;Else
|
|
BEQ STKRTS ;Return FALSE if LSB = 0
|
|
STKTRU: LDA #$FF ;Else Return TRUE
|
|
RTS
|
|
|
|
;stkdrp(&m) - Drop Top Entry from Stack
|
|
;Note: Aborts Calling Routine if Error
|
|
;Uses: STKSLO, STKSHI = Stack Start Address
|
|
;Sets: TEMP1, TEMP2 = Original Stack Pointer
|
|
;Updates: STKLO, STKHI = Stack Pointer
|
|
;Affects: Y,C,N,Z
|
|
;Returns: A=Number of Bytes in Entry
|
|
; 0=Error: Stack Underflow
|
|
; Y=0
|
|
STKDRP: JSR STKSSP ;Save Stack Pointer
|
|
STKDRN: JSR STKCMP ;If Stack Pointer
|
|
BCC STKRPA ; <= Stack Start
|
|
BEQ STKRPA ; Return 0
|
|
JSR STKDEC ;Decrement Stack Pointer
|
|
LDY #0 ;Initialize Index
|
|
LDA (STKLO),Y ;Get Number of Bytes in Entry
|
|
;and fall into STKSUB
|
|
|
|
;stksub(n) - Reduce Stack Pointer by A
|
|
STKSUB: STA TEMP0 ;Save Number in TEMP0
|
|
LDA STKLO
|
|
SEC ;Subtract A from LSB
|
|
SBC TEMP0
|
|
STA STKLO
|
|
LDA STKHI ;Subtract 0 from LSB
|
|
SBC #0 ;For Borrow
|
|
STA STKHI
|
|
JSR STKCMP ;If Stack Pointer < Start
|
|
BCC STKRPA ; Restore Pointer and Return 0
|
|
STKSUE: LDA TEMP0 ;Retrieve Number of Bytes
|
|
RTS
|
|
STKRPA: JSR STKRSP ;Restore Stack Pointer
|
|
STKABT: PLA ;Drop Return Address from Stack
|
|
PLA ; Aborting Calling Routine
|
|
STKZRO: LDA #0 ;Set A to 0
|
|
RTS
|
|
|
|
;stkpop(&m) - Pop Top Entry off Stack
|
|
;Args: Y,X = Address of Source Array
|
|
;Uses: STKSLO, STKSHI = Stack Start Address
|
|
;Updates: STKLO, STKHI = Stack Pointer
|
|
;Affects: C,N,Z
|
|
;Returns: A,Y = Number of Bytes in Entry
|
|
; 0 = Error: Stack Underflow
|
|
STKPOP: JSR SETDST ;Set Destination Address
|
|
JSR STKDRP ;Deallocate Stack Entry
|
|
STKPOS: JSR STKSRC ;Set Source Address to Stack Pointer
|
|
JMP MEMCPL ;Copy Bytes and Return
|
|
|