Date   : Sat, 16 Sep 2006 07:25:59 +0100
From   : Sprow <info@...>
Subject: Re: smartwatch

In article <004301c6d841$cbf43190$0701a8c0@...>,
   Bob Devries <bdevries@...> wrote:
> Sprow said:

> > I think the underwhelming responses to your question are probably mainly
> > because you didn't define what "Smartwatch" was.
> >
> Sorry about that.
> A SmartWatch is a chip made by Dallas Semiconductor. It's a real-time 
> clock.
> Some of them were made to fit underneath a ROM chip. I thought that since 
> the Beeb has a plethora of available ROM sockets, *someone* would have 
> implemented a driver for one of these. The Maxim/Dallas DS1216 is supplied 
> in a 28 pin socket, into which the ROM chip can be piggy-backed.

Right, now I see.
I actually designed something pretty similar myself, but decided to axe the
project when there was little interest shown in it.

Basically, it was a ROM sized PCB (a little like the reprogrammable speech
upgrade) with 
  a PCB mounted battery holder for a coin cell
  a small PAL or similar for address decoding
  an I2C bus
  a DS1307 and crystal like MiniB uses

The address decoding was such that a few byte wide window was opened up high
up in the ROM and you could read/write to the I2C bus by devious addressing.
This got round the absence of a write strobe line on the ROM sockets (since
the data bus from the 6502 goes direct to the ROM sockets the data would be
valid, just not qualified by WE).

It seems however that Dallas have virtually the same thing ready made
(though the battery can't be changed). You'd want to check the pinout
carefully but a cursory glance suggests it should be fine, and I'm quite
tempted to knock up a ROM.

In answer to your original question, no, 
Sprow.