Re: Screen memory mapping VIC-20

From: Jim Brain <>
Date: Sat, 8 Jul 2017 22:54:26 -0500
Message-ID: <>
On 7/7/2017 7:08 AM, Pasi 'A1bert' Ojala wrote:
> On 07.07.2017 14:12, Anders Carlsson wrote:
>> For a long while there was a misunderstanding about the VR/W signal 
>> on the bus that it would be for video R/W but it is not, it is just a 
>> bad naming convention of the signal.
> As far as I remember off-hand, the VR/W is indeed the VIC-I R/W 
> signal. The problem is that the cartridge port only carries the 6502 
> databus, not the part of the bus that it shares with VIC-I. I.e. 
> during a VIC-I access the cartridge databus is separated from the 
> video databus.
> -Pasi
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It is, but it is a preferred signal to use in lieu of CR/W.  I believe 
VR/W is gated with PHI, and so is a cleaner signal to use.


Jim Brain

       Message was sent through the cbm-hackers mailing list
Received on 2017-07-09 04:00:02

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