Date   : Sat, 04 Dec 2004 23:54:00 +0100
From   : John Kortink <kortink@...>
Subject: Re: Eprom programming problem

On Sat, 4 Dec 2004 21:53:38 -0000, "John & Helen Simpson" wrote:

>Thanks for the various tips guys, I'll get hold of some 27128s and try
>those.
>
>Angus - my 27C128 has a Vpp of 12.5v, this seems to be the standard
>nowadays.

Has been for over ten years, really ...

>However, from what I have read on the net I am not sure that
>simply changing the programming voltage is enough. I think the 5v supply
>may also have to be increased to 6v for the duration of the programming.

I've made my own EPROM programmers since 1982, and it's
very rare for the increased 'Vcc' to be necessary. Most
EPROMs program fine at a regular Vcc of 5V and a Vpp of
12V (officially 12.5, 12.75 or 13 depending on the make
of EPROM).


John Kortink

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