passport/src/memory.a

;-------------------------------
; CopyMemory
; in:  A = source address (high)
;      X = destination address (high)
;      Y = number of pages to copy
; out: all flags and registers clobbered
;-------------------------------
!zone {
CopyMemory
         sta   .source+2
         stx   .dest+2
         ldx   #$00
.source  lda   $FF00,x
.dest    sta   $FF00,x
         inx
         bne   .source
         inc   .source+2
         inc   .dest+2
         dey
         bne   .source
         rts
}

;-------------------------------
; ClearMemory
; in:  A = source address (high)
;      X = value to set
;      Y = number of pages
; out: all flags and registers clobbered
;-------------------------------
!zone {
ClearMemory
         sta   .dest+2
         txa
         ldx   #$00
.dest    sta   $FF00,x
         inx
         bne   .dest
         inc   .dest+2
         dey
         bne   .dest
         rts
}

;-------------------------------
; ClearTSBuffer
; clear the $1000 byte memory buffer
; used to store the current track's data
; in:  none
; out: all flags and registers clobbered
;-------------------------------
ClearTSBuffer
         lda   #BASEPAGE
         ldx   #$00
         ldy   #$10
         jmp   ClearMemory

;-------------------------------
; SwapMemory
; in:   A = source address (high)
;       X = destination address (high)
;       Y = number of pages to copy
; out:  all flags and registers clobbered
;-------------------------------
!zone {
SwapMemory
         sta   .source1+2
         sta   .source2+2
         stx   .dest1+2
         stx   .dest2+2
         ldx   #$00
.source1 lda   $FF00,x
         pha
.dest1   lda   $FF00,x
.source2 sta   $FF00,x
         pla
.dest2   sta   $FF00,x
         inx
         bne   .source1
         inc   .source1+2
         inc   .source2+2
         inc   .dest1+2
         inc   .dest2+2
         dey
         bne   .source1
         rts
}

;-------------------------------
; SaveProDOS
; saves memory pages used by ProDOS
; pages $00, $03, $BF
; in:  none
; out: all flags and registers clobbered
;-------------------------------
!zone {
SaveProDOS
         lda   #$00
         ldx   #$40
         ldy   #$01
         jsr   CopyMemory
         lda   #$03
         ldx   #$41
         ldy   #$01
         jsr   CopyMemory
         lda   #$BF
         ldx   #$42
         ldy   #$01
         jsr   CopyMemory
.exit
         rts
}

;-------------------------------
; SwapProDOS
; saves/restores memory pages used by ProDOS
; pages $00, $03, $BF
; in:  none
; out: all flags and registers clobbered
;-------------------------------
SwapProDOS
         lda   #$00
         ldx   #$40
         ldy   #$01
         jsr   SwapMemory
         lda   #$03
         ldx   #$41
         ldy   #$01
         jsr   SwapMemory
         lda   #$BF
         ldx   #$42
         ldy   #$01
         jsr   SwapMemory
         rts