[Coco] DRAGON TANO Arrived

[Gene Heskett]

On Monday 01 October 2012 17:26:13 Ciaran Anscomb did opine:

> Juan Castro wrote:
> > I don't know much about the Dragon differences. Does it have RS-232 by
> > other means?
> 
> Yes, the Dragon 64 (and thus the Tano Dragon) has an ACIA.  I gather
> people have managed to drive the CoCo bit banger faster than the ACIA
> can reliably transfer data though (odd as that sounds, and I might have
> got some facts mixed up there).  Mind you, easier to use the ACIA...
> 
> ..ciaran
 
A couple points of interest here.  I don't want to disparage the ACIA, but 
generally speaking, its total lack of a buffer makes it far less than 
useful for this.  Its maximum speed is 9600 baud under most conditions, and 
because of the lack of a buffer, (what buffer it has is in the driver, not 
in the chip) any time the interrupts are disabled while a disk write is 
being done, will generally cause a framing error.

Toss in that with the current driver, there is no usable flow control, as 
neither the usual 7 wire hardware protocol, or the xon/xoff is usable. 17 
years ago, we did have a usable driver, but either the code or the docs 
have not kept pace.  I have tried to pull in the old driver & descriptor 
and restore that, but have not been successful, primarily because (I think) 
the coupling to the scf driver has been changed.

Now, I may be full of it, but if someone can document both the xmode 
options to use, and the cable wiring so as to make the 7-wire protocol work 
with todays driver, I would be very grateful to be proven wrong.

The bit-banger, with the drivewire protocol, can run at 115kbaud, or even 
230kbaud, corresponding to about 10 to 20k a second, and apparently has a 
pretty robust flow control.

DriveWire handles all the gritty details, and hides them pretty well.  Not 
to mention its faster.

Cheers, Gene
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