Re: How to properly use a 74259 (addressable latch)

From: Tam/WB2TT (t-tammaru_at_c0mca$t.net)
Date: 01/26/05 

Date: Wed, 26 Jan 2005 10:57:16 -0500

"sryth" <sryth@yahoo.com> wrote in message
news:1106707934.008771.32480@c13g2000cwb.googlegroups.com...
>I am thinking of connecting a 74259 (8-bit addressable latch) to a
> USBMOD4 device to ultimately control 8 mosfets. The data sheet for the
> latch said that you should hold pin G high while changing address lines
> to avoid mangling your stored values, and I'm trying to come up with an
> elegant solution.
>
> My device sets all 8 data lines "simultaneously"; I need to ensure that
> the line connected to the enable doesn't drop until the address/data
> lines are set up.
>
> I was thinking of a simple RC circuit sent into an schmitt inverter to
> delay the dropping of G for ~100ms...would this work reliably? Are
> there better ways of doing this?
>

This used to be one of my favorite parts. I always made WR* or DS* as part
of the Chip Select. You just have to be sure you end up with enough Address
and Data hold time.

Tam

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