[Coco] Printing from DW

[Al Hartman]

I used to have a Disto Super Controller. I loaned it to Zebra Systems for 
writing drivers to support it for CGDP and Zebra Write. But, it got lost and 
I never saw it again.

I wish Tony would release the artwork so we could make a run of them. I'd 
love to have one again. I wish someone would make a clone FD-502 Controller 
PCB. They come up on eBay every so often, but eventually they will become 
quite rare. Especially if it had a built-in ROM switch so we could switch 
between HDB-DOS and DECB or ADOS. And, if it had the high density mod 
built-in, that would be a nice boon for Coco users. Imagine using 1.44mb 
drives and floppies on a Coco...

-[ Al ]-

-----Original Message----- 
From: Gene Heskett
Sent: Monday, October 27, 2014 1:50 PM
To: coco at maltedmedia.com
Subject: Re: [Coco] Printing from DW

On Monday 27 October 2014 11:35:47 Al Hartman did opine
And Gene did reply:
> In "Turn of the Screw" there is a Parallel Port Cartridge.
>
> If someone made up the board for it, I'd love to build a couple.
>
> Couldn't an OS9/NitrOS9 driver be written for it, and then the printing
> problem would be solved. He already provides patches for DECB.
>
> -[ Al ]-

Someplace in my midden heap of code is a very simple driver for the
parport on the side of either the 4n1, or J&M-CP controllers.  I can post
it if I can find it, probably on my web page.

But it has one very glaring problem.  When the FCC mandated in the mid
80's the radiated noise level controls, most printers including our
miserable but beloved DMP's, had enough filtering applied to their parport
inputs that the only way to actually write to a parallel printer would
have been to add a timer circuit someplace in the controller that was
triggered by the /cs at the port pin called strobe, and which fired off
pulling the halt line back to the 6x09 low while the data strobe was
active, thereby freezing the 6x09 in the write cycle for 5 to 10
microseconds, giving the data time to get thru the filters and into the
printer.

I have both controllers, but never managed to find a suitable round tuit.
Then I got a decent serial printer and never looked back.

But now all you hardware guru's know what you have to do to make it work
well.

There is a second alternative too, and that would be to add an 8 bit wide
latch chip (74HCT245?) in the cable, again with a timer to hold the data
stable for a few microseconds and then clear the strobe back high until
the next byte is written. There may be enough lag between bytes sent that
no time killers would be needed in the driver. That would be the
preferable method in fact. That has the slight disadvantage of needing a
few milliamps of 5 volts from someplace.  Schottky diodes off the data
lines could probably steal enough power for HC chips.  The printers inputs
would be the major load.

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>
US V Castleman, SCOTUS, Mar 2014 is grounds for Impeaching SCOTUS

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