Re: BASIC and System ROM replacements

From: Jim Brain <>
Date: Thu, 30 May 2013 01:22:46 -0500
Message-ID: <>
On 5/29/2013 9:55 AM, Gerrit Heitsch wrote:
> On 05/27/2013 07:57 AM, Baltissen, GJPAA (Ruud) wrote:
>> Hallo JG,
>>> Something I'd find useful is being able to have more than 16K
>>> available in the 16K cartridge slot, and to be able to page
>>> the cartridge out. Then I could copy greater than 16K code
>>> from the cartridge to RAM, than page out the cartridge.
>> A 27512 EPROM can handle 64 KB. A 74LS273, a resetable latch, can 
>> handle the pages plus 'paging out' the cartridge.
> Another useful TTL in that respect is the 74LS175. It's used in the 
> banking logic of the 264 series. It only has 4 Bits instead of 8 but 
> all of them are available as normal and inverted.
>  Gerrit
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Speaking (writing) of bank registers, anyone know of a TTL option that 
has a falling edge trigger?  Yes, I can do an inverter, but would rather 
not.  Use case is VIC-20, which won't work on rising edge of Phi, 
because not all of the data is valid on rising edge.


Jim Brain

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Received on 2013-05-30 07:00:02

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