Re: LCD64 Update /Help

From: Marko Mäkelä (
Date: 2001-03-09 08:03:22

On Fri, 9 Mar 2001 wrote:

> Any other suggestions for chips which could be off-lined or swapped to save
> a few mA?

The $dd00 CIA can be removed from the board altogether if you don't need
the user port or the serial bus.  Many programs don't switch the 16k video
bank from its default location (0-$3fff), so you don't need the chip for
that either.

For mass storage (or even for replacing the KERNAL/BASIC ROM), you could
use a Flash ROM. AMD Am29LV160D looks quite promising.  Its only
disadvantage for this project is that its operating voltage power supply
must be between 2.7 and 3.6 volts.  You'd require some address and data
bus buffers, e.g. the Texas Instruments SN74LVC244A. The VIC-20 all-in-one
cartridge I and a couple friends of mine are developing will probably use
this chip.  It doesn't require a special voltage for programming or
erasing; you just have to write a "magic cookie" to certain addresses to
enable the programming mode.

An even wilder thought would be to use 3.3-volt programmable logic, such
as the Lattice 2032 (or bigger), for replacing the 6510 and the PLA.  By
using static RAM (like two 62256's), you wouldn't require any memory
refresh, or any VIC-II.  But these improvements would probably require a
completely redesigned circuit board.


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