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Used I/O mirror locations that avoid (redirected) zero-page accesses.

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This commit is contained in:
Greg King
2015-09-29 12:39:58 -04:00
committed by Oliver Schmidt
parent c39d07dd17
commit 203200e259
6 changed files with 17 additions and 15 deletions
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10
asminc/pce.inc
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@@ -34,11 +34,13 @@ VDC_LENR = 18 ; (DMA) Length Register
VDC_SATB = 19 ; Sprite Attribute Table
; VDC port
; Note: absolute addressing mode must be used when writing to this port
; Note: The zero-page addressing mode is redirected to page $20.
; Therefore, absolute addressing mode must be used when writing to this port.
; We force it by using mirror locations that are outside of zero page.
VDC_CTRL = $0000
VDC_DATA_LO = $0002
VDC_DATA_HI = $0003
VDC_CTRL := $0200
VDC_DATA_LO := $0202
VDC_DATA_HI := $0203
; huc6260 - Video Color Encoder (vce)