Confused about boot file

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pau1ie
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Confused about boot file

Post by pau1ie » Tue Jun 27, 2017 10:37 pm

I am trying to get Dart by AUCBE to work. The UEF asks you if you have a turtle or not, and then creates a program which you have to save as "DART0" . I saved it to a SSD image, and then tried to create a !BOOT file using

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*BUILD !BOOT
CH."DART0"
<ESC>
When I do shift-break it messes up keyboard input somehow, so the opening screen displays then disappears, then some weird effects occur on the screen.

Is there something obvious I am missing here to make the boot file work? Typing the chain command in by hand works fine.
I'm working on http://bbcmicro.co.uk

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lurkio
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Re: Confused about boot file

Post by lurkio » Tue Jun 27, 2017 11:18 pm

Use the standard bbcmicro.co.uk !BOOT file:

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*BASIC
*FX21,0
CLOSE#0:CHAIN "DART0"
In the case of Dart, it seems to be the *FX21,0 (flush keyboard buffer) that makes the difference -- not sure exactly why.

:idea:

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ctr
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Re: Confused about boot file

Post by ctr » Wed Jun 28, 2017 12:25 am

The break key is function key 10. When you press break the OS puts the (notional) key code for f10 into the keyboard buffer. When a program asks for keyboard input the function key definition is returned one character at a time until it is exhausted. e.g. try typing "*KEY10 HELLO" and pressing break.

Normally when you press break, BASIC shows a prompt and immediately asks the OS for keyboard input. The OS finds the f10 in the keyboard buffer, but f10 isn't defined so nothing happens.

When you press shift+break Dart is loaded and overwrites the function key definition area at &B00-&BFF. The first time Dart asks for keyboard input the OS finds the f10 in the keyboard buffer, and expands it using whatever random stuff Dart has put in the function key definition area.

The *FX21,0 removes the f10 from the keyboard buffer.

This is the usual cause anyway. I haven't looked at Dart.

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flaxcottage
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Re: Confused about boot file

Post by flaxcottage » Wed Jun 28, 2017 10:50 am

Interesting.

Worth bearing in mind, thanks. :D
- John

Why do I keep collecting Acorn gear? I'm going to need a considerably bigger man-cave. :?

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pau1ie
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Re: Confused about boot file

Post by pau1ie » Wed Jun 28, 2017 7:44 pm

Brilliant! That works, and thanks for the explanation.
I'm working on http://bbcmicro.co.uk

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