[Coco] DLOAD (was: Re: Stupid Cassette Port Tricks, (was: Re: Coco and .WAV files))

[Joel Ewy]

So, what's the scoop on DLOAD anyway?  I realize that the Network 2
system uses the cassette port and CLOAD/CSAVE, and I take it that DLOAD
uses the bit-banger port. 

I did a quick search through the contents of this mail list since
sometime in 2006 in Thunderbird for DLOAD and was able to glean and/or
surmise the following:

1.  It is patched out of the CoCo 3 ROM (probably still present in the
actual ROM, but overwritten in RAM on boot by Super ECB stuff?)
2.  It has a reputation as being somehow problematic, difficult to use,
or simply obscure and undocumented?
3.  Nevertheless it can be used and has reportedly been used by at least
two individuals to copy programs to a CoCo from a PC.
4.  Roger Taylor has put high-speed serial transfer code into the
Rainbow IDE that can be loaded onto the CoCo (1, 2) using the DLOAD
command, though the code, once loaded, has nothing more to do with DLOAD
and may not be usable without knowing the secret handshake.  :-)

Questions that still remain for me:
Why is it not documented (or is it documented somewhere other than the
"Getting Started/Going Ahead" books?
How was it meant to be used?  Is there a corresponding DSAVE(M) command
in the CoCo's ROM?  Is there some special protocol that needs to be
observed?  What is involved in using it to copy programs to a CoCo from
a PC (aside from a long wait), and can it be used in the reverse direction?
How does it compare with the cassette port in terms of speed and
reliability?  If the cassette port runs at 1500baud, that may indeed be
faster than the CoCo's ROM routines can reliably run the bit-banger. 
OTOH, the serial port may have an edge in terms of versatility, and you
can use an ordinary cable.

JCE

wdg3rd at comcast.net wrote:
> From: Joel Ewy <jcewy at swbell.net>
>   
>> That's a pretty cool use for the cassette port, Mike.  I'm sure others
>> have done, or at least thought of this before, but how well would it
>> work (aside from being slow) to csave/cload between two CoCos using a
>> null-cassette cable?  I guess if it can be done over a phone line, it
>> should be doable with just a cable.  I guess one issue is that with a
>> real cassette player the CoCo can pause the cassette motor, but it
>> wouldn't be able to pause another CoCo.  For simple, single program
>> files, this isn't critical, but some programs pause and restart the
>> cassette while loading, and if the data doesn't pause the program load
>> fails.  I found that out trying to load "The Glove" from an .MP3
>> player.  I'd like to get another cheap one that I can hack up, allowing
>> the CoCo to control the Pause/Play button with the motor relay.
>>
>> Other than that, why shouldn't it work with a suitable cassette
>> crossover cable?  I have more CoCos than mass storage units.  The
>> cassette port could make a serviceable ultra-cheap, low-speed CoCo network.
>>     
>
> I know damned well I'm not the only person on this list who remembers the old Network 1 and Network 2 systems from Tandy.  The Network 1 was only functional with the Model 1 (or the Model 3/4 in slow speed), the Network 2 worked with every Tandy machine that had a cassette port including the Mod 100.  I had them in my RSCC classrooms for five and a half years.  Probably dumped a gig of data through them (which is not impressive now in the days of cable internet porn, but in the early 80s at 500/1500 bps was a lot).
> --
> Ward Griffiths    wdg3rd at comcast.net
>
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