JMP   COMMONX
*
*-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=*
*                              *
*       COMMON.LIB             *
*                              *
* AUTHOR:  NATHAN RIGGS        *
* CONTACT: NATHAN.RIGGS@       *
*          OUTLOOK.COM         *
*                              *
* VERSION: 0.1.2               *
* DATE:    30-OCT-2018         *
* ASSEMBLER: MERLIN 8 PRO      *
*                              *
* LICENSE: APACHE 2.0 LICENSE  *
* WHEN APPLICABLE. CODE        *
* INSPIRED BY THE WORKS OF     *
* OTHERS MAY FALL UNDER A      *
* DIFFERENT LICENSE.           *
*                              *
* COMMON ASM ROUTINES          *
* LIBRARY FOR FUNCTIONS SUCH   *
* AS MEMORY SWAPPING.          *
*                              *
*------------------------------*
*                              *
* LIST OF ROUTINES             *
*                              *
* MEMFILL : FILL LOCATION WITH *
*           A SINGLE VALUE.    *
*                              *
* MEMMOVE : MOVE A BLOCK OF    *
*           MEMORY FROM ONE    *
*           LOC TO ANOTHER.    *
*                              *
* DELAYMS : DELAY FOR A NUMBER *
*           OF MILLISECONDS.   *
*           THIS DEPENDS ON    *
*           THE ACTUAL SYSTEM  *
*           BEING USED, SO     *
*           ISN'T AS EASILY    *
*           PORTED TO OTHER    *
*           6502 SIBLINGS.     *
*                              *
* ZSAVE : SAVE STATE OF FREE   *
*         ZERO PAGE LOCATIONS  *
*         AT MEM LOC SPECIFIED *
*                              *
* ZLOAD : LOAD PREVIOUS SAVED  *
*         ZERO PAGE VALUES     *
*         BACK INTO PROPER     *
*         LOCATION.            *
*                              *
*-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=*
*
*``````````````````````````````*
* MEMFILL :: FILL MEMORY LOC   *
*-                            -*
* FILLS A BLOCK OF MEMORY WITH *
* THE SPECIFIED VALUE; USED    *
* OFTEN TO CLEAR LARGE BLOCKS. *
*-                            -*
* CLOBBERS:                    *
*                              *
* FLAGS:  ????----  REG: AXYM  *
*-                            -*
* CYCLES: ???                  *
* SIZE:                        *
*-                            -*
* USAGE:                       *
*                              *
*     LDA  #>$6A00             *
*     PHA                      *
*     LDA  #<$6A00             *
*     PHA                      *
*     LDA  #>1024              *
*     PHA                      *
*     LDA  #<1024              *
*     PHA                      *
*     LDA  #0                  *
*     PHA                      *
*     JSR  MEMFILL             *
*-                            -*
* ENTRY                        *
*                              *
* TOP OF STACK                 *
*                              *
* LOW BYTE OF RETURN ADDRESS   *
* HI BYTE OF RETURN ADDRESS    *
* FILL VALUE FOR MEMORY        *
* ARRAY SIZE                   *
* LOW BYTE OF STARTING POINT   *
* HIGH BYTE OF STARTING POINT  *
*-                            -*
* EXIT                         *
*                              *
* TOP OF STACK                 *
*                              *
* LOW BYTE OF RETURN ADDRESS   *
* HI BYTE OF RETURN ADDRESS    *
*                              *
*   Y = COUNTER; TRASH         *
*   X = COUNTER; TRASH         *
*   A = LOW BYTE OF RET ADDR   *
*-                            -*
* ADAPTED FROM LEVANTHAL AND   *
* WINTHROP'S /6502 ASSEMBLY    *
* LANGUAGE ROUTINES/.          *
* AS SUCH, THIS MAY NOT FALL   *
* UNDER THE APACHE 2.0 LICENSE *
* AGREEMENT, SINCE THE BOOK    *
* WAS WRITTEN BEFORE THE       *
* LICENSE!                     *
*                              *
* THAT SAID, LEVENTHAL WROTE   *
* THAT THE PURPOSE OF THE BOOK *
* WAS TO COPY THE SOURCE CODE, *
* AS REINVENTING THE WHEEL IS  *
* TEDIOUS, AND HE PLACED NO    *
* RESTRICTIONS ON ITS USE.     *
*,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,*
*
MEMFILL
*
** SAVE RETURN ADDRESS
*
         PLA
         STA   :RETADR
         PLA
         STA   :RETADR+1
*
** GET PARAMETERS
*
         PLA
         STA   :VALUE
         PLA
         STA   :ARYSZ
         PLA
         STA   :ARYSZ+1
         PLA
         STA   ADDR1      ; ZERO PAGE POINTER
         PLA              ; DEFINED IN
         STA   ADDR1+1    ; DECS
*
** FILL WHOLE PAGES FIRST
*
         LDA   :VALUE     ; GET VAL FOR FILL
         LDX   :ARYSZ+1   ; X=# OF PAGES TO DO
         BEQ   :PARTPG    ; BRANCH IF HIGHBYTE OF SZ = 0
         LDY   #0
:FULLPG
         STA   (ADDR1),Y
         INY              ; INC TO NEXT BYTE
         BNE   :FULLPG    ; BRANCH IF NOT DONE W/ PAGE
         INC   ADDR1+1    ; ADVANCE TO NEXT PAGE
         DEX
         BNE   :FULLPG    ; BRANCH IF NOT DONE W/ PAGES
*
** DO THE REMAINING PARTIAL PAGE
** REGISTER A STILL CONTAINS VALUE
*
:PARTPG
         LDX   :ARYSZ     ;GET # OF BYTES IN FINAL PAGE
         BEQ   :EXIT      ; BRANCH IF LOW BYTE = 0
         LDY   #0
:PARTLP
         STA   (ADDR1),Y  ; STORE VAL
         INY              ; INCREMENT INDEX
         DEX              ; DECREMENT COUNTER
         BNE   :PARTLP    ; BRANCH IF NOT DONE
:EXIT
*
** RESTORE RETURN ADDRESS
*
         LDA   :RETADR+1
         PHA
         LDA   :RETADR
         PHA
         RTS
*
** DATA
*
:VALUE   DS    1          ; FILL VALUE
:ARYSZ   DS    2          ; ARRAY SIZE
:RETADR  DS    2
*
*``````````````````````````````*
* MEMMOVE :: MOVE MEM BLOCK    *
*-                            -*
* MOVES A SPECIFIED BLOCK OF   *
* MEMORY FROM A SOURCE ADDRESS *
* TO A DESTINATION ADDRESS     *
* RANGE.                       *
*-                            -*
* CLOBBERS:                    *
*                              *
* FLAGS:  ????----  REG: AXYM  *
*-                            -*
* CYCLES: ???                  *
* SIZE:                        *
*-                            -*
* USAGE:                       *
*                              *
*      LDA #>$6A00             *
*      PHA                     *
*      LDA #<$6A00             *
*      PHA                     *
*      LDA #>$7000 ; DEST      *
*      PHA                     *
*      LDA #<$7000             *
*      PHA                     *
*      LDA #>1024              *
*      PHA                     *
*      LDA #<1024              *
*      PHA                     *
*      JSR MEMMOVE             *
*-                            -*
* ENTRY                        *
*                              *
* TOP OF STACK                 *
*                              *
* LOW BYTE OF RETURN ADDRESS   *
* HI BYTE OF RETURN ADDRESS    *
* NUMBER OF BYTES TO MOVE      *
* LOW BYTE OF DESTINATION      *
* HIGH BYTE OF DESTINATION     *
* LOW BYTE OF SOURCE ADDRESS   *
* HIGH BYTE OF SOURCE ADDRESS  *
*-                            -*
* EXIT                         *
*                              *
* TOP OF STACK                 *
*                              *
* LOW BYTE OF RETURN ADDRESS   *
* HI BYTE OF RETURN ADDRESS    *
*                              *
*   Y = COUNTER; TRASH         *
*   X = COUNTER; TRASH         *
*   A = LOW BYTE OF RET ADDR   *
*-                            -*
* ADAPTED FROM LEVANTHAL AND   *
* WINTHROP'S /6502 ASSEMBLY    *
* LANGUAGE ROUTINES/.          *
* AS SUCH, THIS MAY NOT FALL   *
* UNDER THE APACHE 2.0 LICENSE *
* AGREEMENT, SINCE THE BOOK    *
* WAS WRITTEN BEFORE THE       *
* LICENSE!                     *
*                              *
* THAT SAID, LEVENTHAL WROTE   *
* THAT THE PURPOSE OF THE BOOK *
* WAS TO COPY THE SOURCE CODE, *
* AS REINVENTING THE WHEEL IS  *
* TEDIOUS, AND HE PLACED NO    *
* RESTRICTIONS ON ITS USE.     *
*,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,*
*
MEMMOVE
*
*
** SAVE RETURN ADDRESS
*
         PLA
         STA   :RETADR
         PLA
         STA   :RETADR+1
*
** GET PARAMETERS
*
         PLA
         STA   :MVELEN
         PLA
         STA   :MVELEN+1
         PLA
         STA   ADDR2      ; ZERO PAGE POINTER
         PLA
         STA   ADDR2+1
         PLA
         STA   ADDR1
         PLA
         STA   ADDR1+1
*
** DETERMINE IF DEST AREA IS
** ABOVE SRC AREA BUT OVERLAPS
** IT. REMEMBER, OVERLAP CAN BE
** MOD 64K. OVERLAP OCCURS IF
** STARTING DEST ADDRESS MINUS
** STARTING SRC ADDRESS (MOD
** 64K) IS LESS THAN NUMBER
** OF BYTES TO MOVE.
*
         LDA   ADDR2      ;CALC DEST-SRC
         SEC
         SBC   ADDR1
         TAX
         LDA   ADDR2+1
         SBC   ADDR1+1    ; MOD 64K AUTOMATIC
                          ; -- DISCARD CARRY
         TAY
         TXA              ; CMP WITH # OF BYTES TO MOVE
         CMP   :MVELEN
         TYA
         SBC   :MVELEN+1
         BCS   :DOLEFT    ; BRANCH IF NO OVERLAP
*
** DEST AREA IS ABOVE SRC AREA
** BUT OVERLAPS IT.
** MOVE FROM HIGHEST ADDR TO
** AVOID DESTROYING DATA
*
         JSR   :MVERHT
         JMP   :EXIT
*
** NO PROB DOING ORDINARY MOVE
** STARTING AT LOWEST ADDR
*
:DOLEFT
         JSR   :MVELEFT
:EXIT
         JMP   :MREXIT
*
********************************
* SUBROUTINE: MVELEFT          *
********************************
*
:MVELEFT
         LDY   #0         ; ZERO INDEX
         LDX   :MVELEN+1  ; X=# OF FULL PP TO MOVE
         BEQ   :MLPART    ; IF X=0, DO PARTIAL PAGE
:MLPAGE
         LDA   (ADDR1),Y
         STA   (ADDR2),Y  ;MOVE ONE BYTE
         INY              ; NEXT BYTE
         BNE   :MLPAGE    ; CONT UNTIL 256B MOVED
         INC   ADDR1+1    ; ADV TO NEXT SRC PAGE
         INC   ADDR2+1    ; ADV NEXT DEST PAGE
         DEX              ; DEC PAGE COUNT
         BNE   :MLPAGE    ; CONT UNTIL ALL FULL
                          ; PAGES ARE MOVED
:MLPART
         LDX   :MVELEN    ; GET LENGTH OF LAST PAGE
         BEQ   :MLEXIT    ; BR IF LENGTH OF LAST
                          ; PAGE = 0
                          ; REG Y IS 0
:MLLAST
         LDA   (ADDR1),Y
         STA   (ADDR2),Y  ; MOVE BYTE
         INY              ; NEXT BYTE
         DEX              ; DEC COUNTER
         BNE   :MLLAST    ; CONT UNTIL LAST P DONE
:MLEXIT
         JMP   :MREXIT
*
********************************
* SUBROUTINE: MVERHT           *
********************************
*
:MVERHT
*
** MOVE THE PARTIAL PAGE FIRST
*
         LDA   :MVELEN+1
         CLC
         ADC   ADDR1+1
         STA   ADDR1+1    ;POINT TO LAST P OF SRC
         LDA   :MVELEN+1
         CLC
         ADC   ADDR2+1
         STA   ADDR2+1    ; POINT TO LAST P OF DEST
*
** MOVE THE LAST PARTIAL PAGE FIRST
*
         LDY   :MVELEN    ;GET LENGTH OF LAST PAGE
         BEQ   :MRPAGE    ; IF Y=0 DO THE FULL PAGES
:MR0
         DEY              ; BACK UP Y TO NEXT BYTE
         LDA   (ADDR1),Y
         STA   (ADDR2),Y  ; MOVE BYTE
         CPY   #0
         BNE   :MR0       ; BR IF NOT DONE W LAST P
:MRPAGE
         LDX   :MVELEN+1  ; GET BYTE OF COUNT AS P CT
         BEQ   :MREXIT    ; BR IF HYBYTE = 0 (NO FULL P)
:MR1
         DEC   ADDR1+1    ; BACK UP TO PREV SRC PAGE
         DEC   ADDR2+1    ; AND DEST
:MR2
         DEY              ; BACK UP Y TO NEXT BYTE
         LDA   (ADDR1),Y
         STA   (ADDR2),Y  ; MOVE BYTE
         CPY   #0
         BNE   :MR2       ; BR IF NOT DONE W THIS PAGE
         DEX
         BNE   :MR1       BR IF NOT ALL PAGES MOVED
:MREXIT
*
** RESTORE RETURN ADDRESS
*
         LDA   :RETADR+1
         PHA
         LDA   :RETADR
         PHA
         RTS
*
** DATA
*
:RETADR  DS    2
:MVELEN  DS    2
*
*``````````````````````````````*
* DELAYMS :: DELAY X MILLISECS *
*-                            -*
* DELAYS FOR X NUMBER OF       *
* MILLISECONDS BY LOOPING      *
* THROUGH PRECISELY CALCULATED *
* NUMBER OF CYCLES.            *
*-                            -*
* CLOBBERS:                    *
*                              *
* FLAGS:  ????----  REG: -XY-  *
*-                            -*
* CYCLES: ???                  *
* SIZE:                        *
*-                            -*
* USAGE:                       *
*                              *
*          LDY #250 ;1/4 SEC   *
*          JSR DELAYMS         *
*-                            -*
* ENTRY                        *
*                              *
* Y = NUMBER OF MILLISECONDS   *
*-                            -*
* EXIT                         *
*                              *
*   Y = COUNTER; TRASH         *
*   X = COUNTER; TRASH         *
*   A = UNCHANGED              *
*-                            -*
* ADAPTED FROM LEVANTHAL AND   *
* WINTHROP'S /6502 ASSEMBLY    *
* LANGUAGE ROUTINES/.          *
* AS SUCH, THIS MAY NOT FALL   *
* UNDER THE APACHE 2.0 LICENSE *
* AGREEMENT, SINCE THE BOOK    *
* WAS WRITTEN BEFORE THE       *
* LICENSE!                     *
*                              *
* THAT SAID, LEVENTHAL WROTE   *
* THAT THE PURPOSE OF THE BOOK *
* WAS TO COPY THE SOURCE CODE, *
* AS REINVENTING THE WHEEL IS  *
* TEDIOUS, AND HE PLACED NO    *
* RESTRICTIONS ON ITS USE.     *
*,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,*
*
DELAYMS
*
MSCNT    EQU   $0CA       ; 202 TIMES THROUGH DELAY1
                          ; SPECIFIC TO 1.23 MHZ
                          ; SPEED OF APPLE II
:DELAY
         CPY   #0         ; 2 CYCLES
         BEQ   :EXIT      ; 2C (EXIT IF DEL=0)
         NOP              ; 2 CYCLES (MAKE OVERHEAD=25C)
*
** IF DELAY IS 1MS THEN GOTO LAST1
** THIS LOGIC IS DESIGNED TO BE
** 5 CYCLES THROUGH EITHER ATH
*
         CPY   #1         ; 2 CYCLES
         BNE   :DELAYA    ; 3C IF TAKEN, ELSE 2C
         JMP   :LAST1     ; 3C
*
** DELAY 1 MILLISENCOND TIMES (Y-1)
*
:DELAYA
         DEY              ; 2C (PREDEC Y)
:DELAY0
         LDX   #MSCNT     ; 2C
:DELAY1
         DEX              ; 2C
         BNE   :DELAY1    ; 3C
         NOP              ; 2C
         NOP              ; 2C
         DEY              ; 2C
         BNE   :DELAY0    ; 3C
:LAST1
*
** DELAY THE LAST TIME 25 CYCLES
** LESS TO TAKE THE CALL, RETURN,
** AND ROUTINE OVERHEAD INTO
** ACCOUNT.
*
         LDX   #MSCNT-3   ; 2C
:DELAY2
         DEX              ; 2C
         BNE   :DELAY2    ; 3C
:EXIT
         RTS              ; 6C
*
*
*``````````````````````````````*
* ZSAVE :: SAVE 0-PAGE FREE    *
*-                            -*
* STORES THE VALUES IN THE     *
* LITTLE FREE SPACE ON THE     *
* ZERO PAGE AT AN ALTERNATE    *
* MEMORY LOCATION TO BE        *
* RETRIEVED AND RESTORED AT A  *
* LATER POINT.                 *
*-                            -*
* CLOBBERS:                    *
*                              *
* FLAGS:  ????----  REG: AXYM  *
*-                            -*
* CYCLES: ???                  *
* SIZE:                        *
*-                            -*
* USAGE:                       *
*                              *
*         LDA #>$6A00          *
*         PHA                  *
*         LDA #<$6A00          *
*         PHA                  *
*         JSR ZSAVE            *
*-                            -*
* ENTRY                        *
*                              *
* TOP OF STACK                 *
*                              *
* LOW BYTE OF RETURN ADDRESS   *
* HI BYTE OF RETURN ADDRESS    *
* LOW BYTE OF DESTINATION      *
* HIGH BYTE OF DESTINATION     *
*-                            -*
* EXIT                         *
*                              *
* TOP OF STACK                 *
*                              *
* LOW BYTE OF RETURN ADDRESS   *
* HI BYTE OF RETURN ADDRESS    *
*                              *
*   Y = TRASH                  *
*   X = TRASH                  *
*   A = LOW BYTE OF RET ADDR   *
*,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,*
*
ZSAVE
*
** LOAD ADDR1 ZERO PAGE AREA FIRST,
** SINCE WE'LL BE USING THAT
*
** NOTE THAT THIS SHOULD ALWAYS BE
** $06 AND $07, OR ELSE CODE WILL
** HAVE TO CHANGE.
*
         LDX   ADDR1
         LDY   ADDR1+1
*
** SAVE  RETURN ADDRESS
*
         PLA
         STA   :RETADR
         PLA
         STA   :RETADR+1
*
** GET PARAMETERS
*
         PLA
         STA   ADDR1
         PLA
         STA   ADDR1+1
*
** COPY ZERO PAGE TO SPECIFIED
** NON-ZERO LOCATION (ONLY THE
** FREE ONES..)
*
         TYA              ; STORE ADDR1 VALS
         LDY   #1         ; FIRST
         STA   (ADDR1),Y
         LDY   #0
         TXA
         STA   (ADDR1),Y
         LDY   #2
         LDA   $08
         STA   (ADDR1),Y
         INY
         LDA   $09
         STA   (ADDR1),Y
         INY
         LDA   $19
         STA   (ADDR1),Y
         INY
         LDA   $1E
         STA   (ADDR1),Y
         INY
         LDA   $E3
         STA   (ADDR1),Y
         INY
         LDA   $EB
         STA   (ADDR1),Y
         INY
         LDA   $EC
         STA   (ADDR1),Y
         INY
         LDA   $ED
         STA   (ADDR1),Y
         INY
         LDA   $EE
         STA   (ADDR1),Y
         INY
         LDA   $EF
         STA   (ADDR1),Y
         INY
         LDA   $FA
         STA   (ADDR1),Y
         INY
         LDA   $FB
         STA   (ADDR1),Y
         INY
         LDA   $FC
         STA   (ADDR1),Y
         INY
         LDA   $FD
         STA   (ADDR1),Y
         INY
         LDA   $FE
         STA   (ADDR1),Y
         INY
         LDA   $FF
         STA   (ADDR1),Y
*
** RESTORE RETURN ADDRESS
*
         LDA   :RETADR+1
         PHA
         LDA   :RETADR
         PHA
*
         RTS
*
** DATA
*
:RETADR  DS    2
*
*``````````````````````````````*
* ZLOAD :: RESTORE 0-PAGE FREE *
*-                            -*
* RESTORES PREVIOUSLY SAVED    *
* ZERO PAGE VALUES FROM        *
* HIGHER MEMORY LOCATION.      *
* CLOBBERS:                    *
*                              *
* FLAGS:  ????----  REG: AXYM  *
*-                            -*
* CYCLES: ???                  *
* SIZE:                        *
*-                            -*
* USAGE:                       *
*                              *
*        LDA #>$6A00           *
*        PHA                   *
*        LDA #<$6A00           *
*        PHA                   *
*        JSR ZLOAD             *
*-                            -*
* ENTRY                        *
*                              *
* TOP OF STACK                 *
*                              *
* LOW BYTE OF RETURN ADDRESS   *
* HI BYTE OF RETURN ADDRESS    *
* LOW BYTE OF SOURCE           *
* HIGH BYTE OF SOURCE          *
*-                            -*
* EXIT                         *
*                              *
* TOP OF STACK                 *
*                              *
* LOW BYTE OF RETURN ADDRESS   *
* HI BYTE OF RETURN ADDRESS    *
*                              *
*,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,*
*
ZLOAD
*
** SAVE  RETURN ADDRESS
*
         PLA
         STA   :RETADR
         PLA
         STA   :RETADR+1
*
** GET PARAMETERS
*
         PLA
         STA   ADDR1
         PLA
         STA   ADDR1+1
*
** COPY ZERO PAGE TO SPECIFIED
** NON-ZERO LOCATION (ONLY THE
** FREE ONES..)
*
         LDY   #2         ; START 2 AHEAD
         LDA   (ADDR1),Y  ; AND PUT ADDR1
         STA   $08        ; AREA LAST
         INY
         LDA   (ADDR1),Y
         STA   $09
         INY
         LDA   (ADDR1),Y
         STA   $19
         INY
         LDA   (ADDR1),Y
         STA   $1E
         INY
         LDA   (ADDR1),Y
         STA   $E3
         INY
         LDA   (ADDR1),Y
         STA   $EB
         INY
         LDA   (ADDR1),Y
         STA   $EC
         INY
         LDA   (ADDR1),Y
         STA   $ED
         INY
         LDA   (ADDR1),Y
         STA   $EE
         INY
         LDA   (ADDR1),Y
         STA   $EF
         INY
         LDA   (ADDR1),Y
         STA   $FA
         INY
         LDA   (ADDR1),Y
         STA   $FB
         INY
         LDA   (ADDR1),Y
         STA   $FC
         INY
         LDA   (ADDR1),Y
         STA   $FD
         INY
         LDA   (ADDR1),Y
         STA   $FE
         INY
         LDA   (ADDR1),Y
         STA   $FF
*
** NOW GET ZERO PAGE VALUES
** FOR SPACE OCCUPIED BY ADDR; RETURN IN X,Y
*
         LDY   #0
         LDA   (ADDR1),Y
         TAX
         LDA   (ADDR1+1),Y
         TAY
         STX   ADDR1
         STY   ADDR1+1
*
** RESTORE RETURN ADDRESS
*
         LDA   :RETADR+1
         PHA
         LDA   :RETADR
         PHA
*
         RTS
*
** DATA
*
:RETADR  DS    2
*
*
COMMONX  RTS