[sebhc] H8 Tape interface debugging?

[Scott LaBombard]

Hi Dave,

Page 40 of the H8-5 manual (posted to the archives) details an
alignment procedure that you should execute. It doesn't require
any equipment ...only jumpering test points and observing the
on-board LED. The procedure sets the space detector and
PLL circuits ... essential for proper operation I've discovered
in the past.

Also, the usual 'cassette caveats' apply ... adjust tone/volume
until things works reliably (as reliable as this medium can be :)).
You might also try disconnecting from the Record jack (leaving
only Play attached) when attempting to load.

As you note the circuits could be drifting ... but as likely the
tape medium could simply be marginal. 


Scott

----- Original Message ----- 
From: "Dave Dunfield" <dave04a at dunfield.com>
To: <sebhc at sebhc.org>
Sent: Sunday, May 16, 2004 4:15 PM
Subject: [sebhc] H8 Tape interface debugging?


> Hi Guys,
> 
> I fired up my H8 today, and for the first time connected a tape recorder
> and tried to load the software tapes.
> 
> The good news is that the interface appears to "mostly" work - it detects
> the tape and walks through memory as it loads - everything looks right.
> 
> The bad news is that the only tape I could get to load was BUG-8. It
> loads consistantly, while the other programs TED8, HASL8, BHBASIC all
> fail. I've tried various tape volume levels and no joy yet.
> 
> At first I thought this might be because I have only a single 4K memory
> board in my H8 - at least the manual I have says 4K, and there is only
> one memory board, however looking at the SP which is initialized by PAM-8
> suggests there is 8K (it's set to 077,377 = $3FFF, and since memory starts
> at 040,000 ($2000) ... $2000-$3FFF is 8K - the schematic for the RAM board
> calls it a 4k/8k board, so it looks like I have 8K after all.
> 
> I tried keying in the memory test from the beginning of the operation
> manual, setting it for 8K, and it ran with no errors - so I'm pretty
> sure there is 8K of functional RAM in there.
> 
> I also tried dumping memory out to the tape and restoring it. I was
> able to dump/load a few small blocks, however if I try to dump/load a
> large block, it always fails - looks like something is drifting (it's
> worth noting that Bug-8 is the smallest of the Heathkit images).
> 
> Anybody got any hints/suggestions/experiences with debugging the
> H8 tape interface?
> 
> Regards,
> Dave
> -- 
> dave04a (at)    Dave Dunfield
> dunfield (dot)  Firmware development services & tools: www.dunfield.com
> com             Vintage computing equipment collector.
>                 http://www.parse.com/~ddunfield/museum/index.html
> 
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