39 lines
1.2 KiB
ArmAsm
39 lines
1.2 KiB
ArmAsm
;;; -*- Mode: asm; indent-tabs-mode: t; tab-width: 8 -*-
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;;############ HANDLES BIG MEMORY MANAGMENTS ############
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;;Move memory from B_start B_end to A_start , (implied address)
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;; B_start and B_end gets modified under execution.
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.proc memcpy
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A_start = $FAFB
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B_start = $FCFD
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B_end = $FEFF
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;; Let Y + A_start lower nibble represent A_start
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;; therefor: A_start = Y - A_start
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;; With Y we mean what Y will represent later aka >B_start
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Sub_16 >A_start, <A_start, >B_start, #$00
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;;Lets move B_start lover-nibble to Y
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LDY >B_start
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LDA #$00
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STA >B_start
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loop:
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;Lag_16 >B_end, <B_end, >B_start, <B_start, end_loop
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Lag_16y >B_end, <B_end, <B_start, end_loop
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;Lag_16y <B_start, >B_end, <B_end, end_loop ; IF B_end >B_start stop the loop
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LDA (>B_start), Y
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STA (>A_start), Y
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;Tip save time by counting downward, fast to check if Y ==0 // hugo
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INY
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TYA
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CMP #$ff
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BNE loop
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;BPL loop; Branch if Y dont overflow
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;; Fix overflow
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LDY #$00
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INC <A_start
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INC <B_start
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JMP loop
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end_loop:
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RTS
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.endproc
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