Date   : Thu, 03 Dec 2009 13:12:39 +0100
From   : kortink@... (John Kortink)
Subject: Tube - I/O processor memory questions

On Tue, 01 Dec 2009 21:53:56 +0000, Kevin Bracey
<kevin@...> wrote:

>John Kortink wrote:
>
>[...]
>
>> If the language boots from ROM using a *-command, the
>> *-command should probably relay any parameters to the
>> language in its own specific way. 
>But that doesn't work if the language isn't in ROM, and they've just run 
>the image from disc on a coprocessor.

It does if you know which situations applies. It's
just a different method in each case.

>[...]
>   
>Indeed, you do have to skip past the filename/command to a space again, 
>but that's much as a normal service *Command handler. Just with the 
>added overhead of the OSWORD 5.  Just a bit silly that you often end up 
>repeating work your service handler did.

Having to use OSWORD 5 is a bit silly period.

The irony of the situation with OSARGS, of course, is
that it gives you a pointer to a copy of the command
line tail in the I/O processor when, in theory, it
could simply refer to the original in the second
processor. E.g. OSARGS A=1 Y=0 sends back an offset
(based on the last OSCLI commandline pointer), 2p
converts it back to the local address (based on the
last OSCLI commandline pointer).

Something similar happens with OSWORD 0.

>[...]
>
>Should I look for magic words in my workspace? Or is there some definite 
>cue that this is a Break-derived entry?

In theory, C is the discriminator (clear = entered
from reset, set = otherwise, presumably *Run).

In practice, the second processor doesn't give a
<beep>. It only does the required A=1 before
entering. C is invalid.

>[...]
>
>Beginning to wander here on a stream of consciousness, but in the Master 
>case, if they don't deign to give a proper filename, what's my correct 
>response to drop out to a Supervisor prompt? Just do an RTS?

Restore the BRK vector if needed and generate an
error. On the second processor, the default BRK
handler displays the error message and exits to
the supervisor.

>Is that what provokes "Language?" on a BBC?

No, that indicates the absence of a(ny) language ROM.


John Kortink

-- 

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

Those who can, do. Those who can't, manage.