Re: ROMs replacement

From: Gerrit Heitsch <*gerrit_at_laosinh.s.bawue.de*> Date: Mon, 17 Sep 2012 18:44:16 +0200 Message-ID: <50575360.6060503@laosinh.s.bawue.de> · gerrit_at_laosinh.s.bawue.de

On 09/17/2012 12:01 PM, silverdr@wfmh.org.pl wrote:
>
>
> The NAND version looks like this:
>
> https://dl.dropbox.com/u/58002657/rom_replacement_nand.png
>
> It has four pull-up resistors.

You can eliminate 2 of them since a truly unused input can just be tied 
to +5V directly. That means R304 and R301 can be replaced by a direct 
trace to +5V.

The other two you will need though since you have 2 inputs that need to 
be pulled to HIGH through a resistor in order you to be able to pull 
them to GND when needed without shorting the supply. I don't see how 
using a 148 would change that.

  Gerrit

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