Date   : Fri, 25 Jul 2008 17:39:49 +0100
From   : profpep@... (Mike)
Subject: EEPROM writing in SW rom bank?

From: "Ian Wolstenholme"


Just another thought - doesn't the Master Compact have one of these
EEPROMs in it to hold the configuration settings?

The Compact has an 8 pin serial EEPROM - which is wriiten and read in an
entirely different way, the Compact one is an PCD 8572, an  I2C device,
which reads and writes on 2 pins.

As a thought, for the compact it might be possible to fit one of the I2C
clock/memory chips, and I somehow remember an Acorn person once telling me
it was possible, but not fitted on grounds of cost. Whether the relevent
code is still in the OS is another matter.

||\/||ike





Original Message -----
From: Charlie.Robson@... [mailto:Charlie.Robson@...]
To: bbc-micro@...
Sent: Fri, 25 Jul 2008 10:23:55 +0100
Subject: Re: [BBC-Micro] EEPROM writing in SW rom bank?

"Ian Wolstenholme" <bbcmailinglist@...> wrote on 25/07/2008
09:56:33:

> I'm not sure if this would be possible, or at least, as straightforward
as it
> might appear to sound.  Presumably if you could just plug an EPROM into
> an SROM socket and connect a lead between the write line and pin 8 IC77
> or similar, then there wouldn't have been much of a market for EPROM
> programmers.
> And also, I expect you'd find hundreds of user modified Beebs with
apermanent
> connection made between the two points, and probably a ZIF socket in the
> ROM slot as well so that the user could programme his own EPROMs at
will.

You are indeed correct - for EPROMS. I am using an *EEPROM* which, for the
uninitiated, are writable a _bit_ like RAM, in that you don't necessarily
need to use a programming voltage to cook the bits, plain 'ol 5v will do
it.

You write to the chip as you would a RAM, taking into account any protocol
required to turn off any 'soft' write protection, and then wait until it
takes its requisite time to self-program. You can poll for write
completion
in a number of ways, usually involving reading back the byte you've just
written until bits stop flipping in some manner or other.


C




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OX14 3YP, United Kingdom.

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