Hi, at testing my new CBM2-v9958 graphics card I had a problem to write to the VDP-VRAM. After some non-successful testing with longer delays between reg and vram access, I started my LA and found an interesting fact: The 6509 performs a short read access before it writes with STA(ZP),Y from bank1 to bank15 (screenshot)! I tried again with code in bank15 $0400 using STA absolute,X and the 6509 only writes correctly. I also measured a read from bank1 to 15 and thats only a plain read. My 6509R4 and the 6509R7 have both this "feature" ;) Is this a know bug of the 6509? PS: After setting up the v9958 VRAM-address I write to the VRAM via port #0, but the VDP saw the read access and increases the address counter so that the write-byte land one byte later in the VRAM and I had a displacement by one char on the screen. BTW: The v9958 has 128k dedicated VRAM and does 256x212 with 256 colors, 512x212 with 16 colors, 512x424 interlaced and 256x212 with 19k colors. It also supports 32 sprites, sprites collision detection, hardware commands like higspeed-move, line, pixel, search and H/V-softs-crolling. It has direct RGB output with PAL or NTSC software selectable ans screen adjusta. <http://cbm-hackers.2304266.n4.nabble.com/file/t374762/6509indirect.jpg> ----- greets Christian -- Sent from: http://cbm-hackers.2304266.n4.nabble.com/Received on 2019-01-31 10:00:04
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