Unusual software carriers. (Was :Vinyl Data- Classic Computers )

Pete Turnbull pete at dunnington.plus.com
Wed Oct 8 16:29:24 CDT 2008

On 08/10/2008 21:27, Tony Duell wrote:
> Minor correction. The Acorn teletext adapter, which used the SAA5020 etc 
> chipset did, indeed connect via the 1MHz bus. But the (IMHO) nicer Morley 
> one connected to the User Port.

So it does.  I'd forgotten.

> It had an I2C interface to an SAA5240 
> chip (this teletext decoder used the I2C bus mot only to select the page, 
> etc, but also allowed you to read/write the teletext page memory, so 
> transfering the page to the BBC micro was relatively easy). There was 
> also a CITAC (Computer Interface for Tuning and Control) chip on that I2C 
> bus (I forget which one was used), this was used to select the TV 
> channel, IIRC the Acorn one had 4 preset pots to select the channel, the 
> computer could then select one of 4 channels.

Yes, the tuning on the Acorn one is definitely not one of its stronger 
points!  Apart from only having four presets, which arguably made sense 
in the UK in 1982, they're very fiddly to set.

Pete						Peter Turnbull
						Network Manager
						University of York

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