[Coco] Assembly lang questions

[Gene Heskett]

On Friday 12 October 2018 09:38:34 tim lindner wrote:

> On Thu, Oct 11, 2018 at 6:39 PM Arthur Flexser <flexser at fiu.edu> wrote:
> > This is the difference between how characters are represented in
> > Ascii vs how they are represented in the CoCo's screen memory,
>
> To put this concept in another way...
>
> The CoCo's VDG does not use ASCII as it's internal representation of
> character data.
>
> To speculate, I would assume this is because a big chunk of ASCII is
> unprintable and it would be a waste of character data.
>

Or, to go back to the first helper tool for a tv station that I ever 
wrote, was back when static memory was sold by the byte at about 10 
cents a byte. Circa 1978 or so. The devices video display which I also 
built with 74 family logic and a bag of diodes, was then of course ntsc, 
and 100% text based on a video image of a 7 segment led display, and was 
limited to two numbers with a separating decimal point, 8.8 style. So I 
took the 7 segment images, re-sorted and combined them into nominally 
half the memory it would have taken to hold the ten digits as direct 
images. As it turned out I got all the functions it needed coded, and by 
judicious use of self modifying code, I actually had memory left over.

At a tv station, 10 years is an eon for any piece of gear, and today its 
down to 3 or 4 years.  Seems theres a new, better digital product to 
replace anything they now use, annually if they can afford it.

But no one else has to this day, built a similar device, Microtime 
started to but it disappeared from their tables at the NAB in 10 minutes 
when I commented that I had already done it, with lots more capability 
than their test the market product they had at the NAB a couple years 
later, and it was still in use many times a day when I called them in 
1995 while I was in Salem OR, visiting an aunt who was near the end of 
her ride. Thats 17 years.  To have built something that usable for a tv 
station, and find it was still in use 17 years later, still puts an ear 
to ear grin on my face.

The folks who designed the 6847 may well have resorted to similar tricks.
We'll probably never know. Most of those folks are my generation, and 
many have since passed, taking that knowledge with them.

-- 
Cheers, Gene Heskett
--
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