Date   : Thu, 03 Dec 2009 13:36:36 +0100
From   : kortink@... (John Kortink)
Subject: Tube - I/O processor memory questions

On 03 Dec 2009 00:07:55 +0000, jgh@... (Jonathan Graham
Harston) wrote:

>[...]
>
>> far-fetched to me having just spent ages faffing around using them
>> trying to get my command-line across the Tube. (Or are you going to tell
> 
>http://beebwiki.jonripley.com/Reading_command_line

Um, OSWORD 5 does not auto-increment the address ...

If you do a quick scribble in a Wiki, better check
it first.

>[...]
> 
>You parse your startup command at the *command stage, and bomb out
>with an error there, *NOT* at the language entry stage. Once the
>language has been entered, the language is responsible for handling
>all and every error ganerated.

Sort of. It can still perform a boot check and bail
out with an error, as long as it restores the default
BRK vector first (the handler in a previously running
language is likely to have been overwritten by then).

>[...]
> 
>Kevin Bracey wrote:
>> > Entry is with C=0 for reset triggered start (hard/soft/power on).
>>
>> Doesn't seem to, sadly. Experiments show C set in both cases on the
> 
>Checking the code shows C to be set when entering an image either
>at Break or of as a result of OSBYTE 142 or a *command, so C=0 can
>be seen to mean "entered a break on the I/O processor", and C=1 can
>be seen to mean "not ^ ^ ^ ^ ^".

Unfortunately on a 6502 second processor C is undefined.

>[...]
> 
>> distinction between *RUNning and restarting after Break. The Tube seems
>> to try to re-enter the last thing you *RAN (*RUNned?) after a Break; not
>> something I've seen documented.
> 
>It's in the various Tube documentation. On Soft Break the last CAO
>(Currently Active Object - code with an image header, the same as a
>ROM header) will be re-entered.

That's nonsense. A language doesn't need to have
a ROM header. If it has one, it is validated, but
that is all.


John Kortink

-- 

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Homepage : http://www.inter.nl.net/users/J.Kortink

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