mirror of
https://github.com/lscharen/iigs-game-engine.git
synced 2024-11-26 07:49:17 +00:00
Remove dead code and fix right edge of BG1 rendering
This commit is contained in:
Lucas Scharenbroich
parent
abfcde54c2
commit
62233d4abc
@ -146,176 +146,6 @@ FillScreen lda #0
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bcc :yloop
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rts
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; Set the starting line of the virtual buffer that will be displayed on the first physical line
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; of the playfield.
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;
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; A = line number [0, 207]
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;
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; There are a few things that need to happen with the Y-position of the virtual buffer is changed:
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;
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; 1. The address of the stack in the code fields needs to be changed
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; 2. The entry point into the code field needs to be set
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; 3. The (old) return code needs to be removed
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; 4. The new return code needs to be inserted after the last line
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;
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; If there is a second background, then the Y-register value in the code field needs to
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; change as well, but that is deferred until later because we don't want to duplicate work
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; if both the BG0 Y-position and the BG1 Y-position is changed on the same frame.
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;
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; We have routines that operate on a single blitter bank at time, so we need to break up the loop
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; into blocks of code aligned mod 16. There is some housekeeping because the height of the screen
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; could be less that one full bank.
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;
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; Each of the within-bank subroutine takes the following arguments
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;
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; X = number of lines * 2, 0 to 32
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; Y = starting line * $1000
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; A = value
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;
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; The pseudo-code for this subroutine is as follows.
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;
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; pre_line_count = 0
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; curr_bank = StartY / 16
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;
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; // If the start is not bank aligned, then calculate the pre-work
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; start_mod_16 = StartY % 16
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; if (start_mod_16 !== 0) {
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; pre_line_count = min(16 - start_mod_16, ScreenHeight)
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; do_action(curr_bank, start_mod_16, pre_line_count)
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; curr_bank = (curr_bank + 1) % 13
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; }
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;
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; line_count = ScreenHeight - pre_line_count
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; while (line_count > 16) {
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; do_action(curr_bank, 0, 16)
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; line_count -= 16
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; curr_bank = (curr_bank + 1) % 13
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; }
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;
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; if (line_count > 0) {
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; do_action(curr_bank, 0, line_count)
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; }
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; Helper function to return the address of a specific blitter code field line
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;
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; Input: A = line number [0, 207]
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; Output: A = low word, X = high word
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GetBlitLineAddress
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asl
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tay
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lda BTableLow,y
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ldx BTableHigh,y
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rts
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lines_left ds 2
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start_mod_16 ds 2
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tblptr ds 2
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stksave ds 2
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SetYPos sta StartY ; Save the position
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lda ScreenHeight
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sta lines_left
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lda StartY ; Now figure out exactly how many banks we cross by
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and #$000F ; calculating ((StartY % 16) + ScreenHeight) / 16
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sta start_mod_16
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clc
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adc ScreenHeight
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and #$00F0 ; Just keep the relevant nibble
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lsr
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lsr
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lsr
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tax ; Keep the value pre-multiplied by 2
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ldy #0
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jsr PushBanks ; Push the bank bytes on the stack
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brl :out
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; Start of the main body of the function. We need to get a pointer to the correct offset of
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; the RTable to copy screen addresses into the code fields
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lda ScreenY0
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asl
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clc
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adc #RTable
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sta tblptr
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; Check to see where we start. If we are aligned with a code bank, then skip to the
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; fast inner loop. Otherwise do one iteration to get things lined up
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:prologue lda start_mod_16
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beq :body
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_Mul4096 ; Save the offset into the code bank of the
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tay ; first line.
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lda #16 ; Now figure out how many lines to execute. Usually
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sec ; this will just be the lines to the end of the code
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sbc start_mod_16 ; bank, but if the total screen height is smaller than
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cmp ScreenHeight ; the number of lines in the code bank, we need to clamp
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bcc :min_1 ; the maximum value
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lda ScreenHeight
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:min_1 sta tmp4 ; save for updating the counters
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asl
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tax ; do this many lines
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lda tblptr ; starting at this address
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plb ; Set the code field bank
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jsr CopyFromArray2 ; Copy the right screen edge addresses
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lda lines_left
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sec
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sbc tmp4
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sta lines_left
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lda tblptr
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clc
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adc tmp4
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adc tmp4
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sta tblptr
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; While the number of lines left to render is 16 or greater, loop
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:body lda lines_left
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cmp #16
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bcc :epilogue
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ldy #0
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ldx tblptr
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:body0 plb ; Set the code field bank
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jsr CopyFromArray2Top ; to bypass the need to set the X register
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txa
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clc
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adc #32
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tax
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lda lines_left
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sec
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sbc #16
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sta lines_left
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cmp #16 ; Repeat the test here to we can skip some
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bcs :body0 ; redundant setup and spill the X register
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stx tblptr ; back into tblptr when done
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:epilogue lda lines_left
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beq :out
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asl ; Y is still zero
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tax
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lda tblptr
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plb ; Set the code field bank
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jsr CopyFromArray2 ; to bypass the need to set the X register
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:out lda stksave ; put the stack back
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tcs
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phk ; Need to restore the current bank
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plb
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rts
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; Special subroutine to divide the accumulator by 164 and return remainder in the Accumulator
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;
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; 164 = $A4 = 1010_0100
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@ -401,71 +231,6 @@ Mod208 cmp #%1101000000000000
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sbc #%0000000011010000
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rts
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; BankYSetup
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;
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; This is the set of function that have to be done to set up all of the code banks
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; for execution when the Y-Origin of the virtual screen changes. The tasks are:
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; Patch out the final JMP to jump to the long JML return code
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;
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; Y = starting line * $1000
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SetReturn lda #$0280 ; BRA *+4
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sta CODE_EXIT,y
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rts
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ResetReturn lda #$004C ; JMP $XX00
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sta CODE_EXIT,y
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rts
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; Fill in the even_exit JMP instruction to jump to the next line (all but last line)
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SetNextLine lda #$F000+{entry_3-base}
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ldy #CODE_EXIT+1
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ldx #15*2
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jmp SetAbsAddrs
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; Copy a series of bank bytes onto the direct page, which we will later point the stack
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; at and use to iterate among the different code banks.
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;
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; Y = starting index * 4
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; X = number of bank
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PushBanks sep #$20
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jmp (:tbl,x)
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:tbl da :bottom-05,:bottom-10,:bottom-15,:bottom-20
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da :bottom-25,:bottom-30,:bottom-35,:bottom-40
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da :bottom-45,:bottom-50,:bottom-55,:bottom-60
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da :bottom-65
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:top lda: BlitBuff+48,y ; These are all 8-bit loads and stores
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sta bstk+13
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lda: BlitBuff+44,y
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sta bstk+12
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lda: BlitBuff+42,y
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sta bstk+11
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lda: BlitBuff+38,y
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sta bstk+10
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lda: BlitBuff+34,y
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sta bstk+9
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lda: BlitBuff+30,y
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sta bstk+8
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lda: BlitBuff+26,y
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sta bstk+7
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lda: BlitBuff+22,y
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sta bstk+6
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lda: BlitBuff+18,y
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sta bstk+5
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lda: BlitBuff+14,y
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sta bstk+4
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lda: BlitBuff+10,y
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sta bstk+3
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lda: BlitBuff+6,y
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sta bstk+2
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lda: BlitBuff+2,y
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sta bstk+1
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lda: BlitBuff,y
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sta bstk
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:bottom rep #$20
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rts
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; Patch an 8-bit or 16-bit valueS into the bank. These are a set up unrolled loops to
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; quickly patch in a constanct value, or a value from an array into a given set of
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; templates.
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@ -506,108 +271,6 @@ SetConst ; Need a blank line here
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sta: $0000,y
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:bottom rts
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; CopyFromArray
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;
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; Copy values from an array with a stride of two bytes into the code field
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;
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; X = number of lines * 2, 0 to 32
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; Y = starting line * $1000
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; A = array address
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CopyFromArray2 pha ; save the accumulator
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ldal :tbl,x
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dec
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plx ; put the accumulator into X
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pha ; push the address into the stack
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rts ; and jump
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:tbl da bottomCFA2-00,bottomCFA2-06,bottomCFA2-12,bottomCFA2-18
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da bottomCFA2-24,bottomCFA2-30,bottomCFA2-36,bottomCFA2-42
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da bottomCFA2-48,bottomCFA2-54,bottomCFA2-60,bottomCFA2-66
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da bottomCFA2-72,bottomCFA2-78,bottomCFA2-84,bottomCFA2-90
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da bottomCFA2-96
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CopyFromArray2Top lda: $001E,x
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sta $F000,y
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lda: $001C,x
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sta $E000,y
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lda: $001A,x
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sta $D000,y
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lda: $0018,x
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sta $C000,y
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lda: $0016,x
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sta $B000,y
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lda: $0014,x
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sta $A000,y
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lda: $0012,x
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sta $9000,y
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lda: $0010,x
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sta $8000,y
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lda: $000E,x
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sta $7000,y
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lda: $000C,x
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sta $6000,y
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lda: $000A,x
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sta $5000,y
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lda: $0008,x
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sta $4000,y
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lda: $0006,x
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sta $3000,y
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lda: $0004,x
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sta $2000,y
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lda: $0002,x
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sta $1000,y
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lda: $0000,x
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sta: $0000,y
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bottomCFA2 rts
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; SetScreenAddrs
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;
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; A = initial screen location (largest)
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; Y = starting line * $1000
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; X = number of lines
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;
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; Automatically decrements address by 160 bytes each line
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SetScreenAddrs sec
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jmp (:tbl,x)
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:tbl da bottomSSA-00,bottomSSA-03,bottomSSA-09,bottomSSA-15
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da bottomSSA-21,bottomSSA-27,bottomSSA-33,bottomSSA-39
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da bottomSSA-45,bottomSSA-51,bottomSSA-57,bottomSSA-63
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da bottomSSA-69,bottomSSA-75,bottomSSA-81,bottomSSA-87
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da bottomSSA-93
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SetScreenAddrsTop sta STK_ADDR+$F000,y
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sbc #160
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sta STK_ADDR+$E000,y
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sbc #160
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sta STK_ADDR+$D000,y
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sbc #160
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sta STK_ADDR+$C000,y
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sbc #160
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sta STK_ADDR+$B000,y
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sbc #160
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sta STK_ADDR+$A000,y
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sbc #160
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sta STK_ADDR+$9000,y
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sbc #160
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sta STK_ADDR+$8000,y
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sbc #160
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sta STK_ADDR+$7000,y
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sbc #160
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sta STK_ADDR+$6000,y
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sbc #160
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sta STK_ADDR+$5000,y
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sbc #160
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sta STK_ADDR+$4000,y
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sbc #160
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sta STK_ADDR+$3000,y
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sbc #160
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sta STK_ADDR+$2000,y
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sbc #160
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sta STK_ADDR+$1000,y
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sbc #160
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sta: STK_ADDR+$0000,y
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bottomSSA rts
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; SetAbsAddrs
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;
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; A = absolute address (largest)
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@ -660,18 +323,20 @@ SetAbsAddrs sec
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;
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; A = high word of bank table
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; Y = index * 4 of the bank to initialize
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bankArray equ tmp0
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target equ tmp2
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nextBank equ tmp4
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BuildBank
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stx bankArray
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sta bankArray+2
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stz target
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:bankArray equ tmp0
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:target equ tmp2
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:nextBank equ tmp4
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stx :bankArray
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sta :bankArray+2
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stz :target
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iny
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iny
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lda [bankArray],y
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sta target+2
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lda [:bankArray],y
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sta :target+2
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iny ; move to the next item
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iny
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@ -679,19 +344,19 @@ BuildBank
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cpy #4*13 ; if greater than the array length, wrap back to zero
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bcc :ok
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ldy #1
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:ok lda [bankArray],y ; Get the middle and high bytes of the address
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sta nextBank
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:ok lda [:bankArray],y ; Get the middle and high bytes of the address
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sta :nextBank
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:next
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jsr BuildLine2
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lda target
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jsr :BuildLine2
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lda :target
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clc
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adc #$1000
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sta target
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sta :target
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bcc :next
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phb
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pei target+1
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pei :target+1
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plb
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plb
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@ -702,10 +367,10 @@ BuildBank
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ldy #$F000+CODE_EXIT ; Patch the last line with a JML to go to the next bank
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lda #{$005C+{TWO_LYR_ENTRY}*256}
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sta [target],y
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sta [:target],y
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ldy #$F000+CODE_EXIT+2
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lda nextBank
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sta [target],y
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lda :nextBank
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sta [:target],y
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plb
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rts
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@ -715,11 +380,11 @@ BuildBank
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;
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; X = low word of address (must be a multiple of $1000)
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; A = high word of address (bank)
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BuildLine
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stx target
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sta target+2
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:BuildLine
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stx :target
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sta :target+2
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BuildLine2
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:BuildLine2
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lda #CODE_LEN ; round up to an even number of bytes
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inc
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and #$FFFE
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@ -728,7 +393,7 @@ BuildLine2
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dec
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tay
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:loop lda base,y
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sta [target],y
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sta [:target],y
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dey
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dey
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@ -738,9 +403,9 @@ BuildLine2
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sep #$20
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ldx #0
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lda target+2 ; patch in the bank for the absolute long addressing mode
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lda :target+2 ; patch in the bank for the absolute long addressing mode
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:dobank ldy BankPatches,x
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sta [target],y
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sta [:target],y
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inx
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inx
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cpx #BankPatchNum
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@ -748,10 +413,10 @@ BuildLine2
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ldx #0
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:dopage ldy PagePatches,x ; patch the page addresses by adding the page offset to each
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lda [target],y
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lda [:target],y
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clc
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adc target+1
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sta [target],y
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adc :target+1
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sta [:target],y
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inx
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inx
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cpx #PagePatchNum
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@ -790,8 +455,8 @@ right_odd bit #$000B ; Check the bottom nibbl
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bne r_is_jmp
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long_1 stal *+4-base
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dfb $00,$00 ; this here to avoid needing a BRA instruction back. So the fast-path
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; gets a 1-cycle penalty, but we save 3 cycles here.
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dfb $00,$00
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bra r_is_pea+1
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r_is_pea xba ; fast code for PEA
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sep #$20
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@ -879,6 +544,7 @@ even_exit jmp $1000 ; Jump to the next line.
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long_4 stal *+4-base
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dfb $00,$00
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xba
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sep #$20
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bra :left_byte
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@ -942,3 +608,10 @@ top
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