Date   : Fri, 05 Nov 2010 00:32:23 +0000
From   : philpem@... (Philip Pemberton)
Subject: Acorn's US patent

On 04/11/10 12:14, Theo Markettos wrote:
> In article<20101104112517.avwht9ff40cg8048@...>  you wrote:
>> Rick Murray wrote:
>>> The other patent is:
>>>     http://www.freepatentsonline.com/5400044.pdf
>>> which describes a method of taking a one bpp LCD display (pixel on or
>>> pixel off) and modulating pixels around plus refresh speeds, to make a
>>> pseudo-greyscale display device out of it.
>>
>> Isn't that how the A4 display worked?
>
> Yes, that's what's implemented in the A4's LCD ASIC.  The A4 TRM mentions
> that it's patented, but I hadn't seen the patent before.

Neither had I, though I've seen the trick applied to a variety of 
displays. By far the most unusual was a Hitachi HD44780-based text 
display...

If I can get my FPGA board successfully tied in, I might have a go at 
doing it with one of my Planar EL displays.

> The A4's display is actually two completely separate panels (top half and
> bottom half) with no gap between them, so the ASIC has to raster scan both
> halves at once.

Some TFTs work the same way -- you either load two adjacent pixels at 
once, or a split image. It's very rare to see one built as two separate 
panels like the A4 was -- you can even see the split due to the slight 
contrast variation.

-- 
Phil.
philpem@...          
http://www.philpem.me.uk/