ACCCON TST

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Pernod
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ACCCON TST

Post by Pernod » Thu Oct 31, 2019 12:42 pm

The Master service manual isn't very clear on which IO is paged out when the ACCCON TST bit is set. A diagram suggests only page &FE is IO/ROM, and there's no other mention of the TST bit.

I see b-em pages out pages &FC,&FD, &FE, which looks more likely as the MOS contains credits in these pages. Does any software/hardware make use of this bit to act as a test case? The only use I can think of is to checksum the MOS.

So which is it, just page &FE or pages &FC,&FD,&FE?
- Nigel

BBC Model B: ATPL Sidewise, Acorn Speech, 2xWatford Floppy Drives, AMX Mouse, Viglen case, BeebZIF, etc.

tom_seddon
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Re: ACCCON TST

Post by tom_seddon » Thu Oct 31, 2019 1:03 pm

MOS 3.50 has code in these pages.

Good point about pages $fc and $fd - I'd always assumed it was all 3 pages that were paged out, but come to think of it I'm not sure I ever actually tested this...

--Tom

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Pernod
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Re: ACCCON TST

Post by Pernod » Thu Oct 31, 2019 1:17 pm

tom_seddon wrote:
Thu Oct 31, 2019 1:03 pm
MOS 3.50 has code in these pages.
I never noticed that before, but would suggest all 3 pages are paged out. Any idea what the code there does?
- Nigel

BBC Model B: ATPL Sidewise, Acorn Speech, 2xWatford Floppy Drives, AMX Mouse, Viglen case, BeebZIF, etc.

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jgharston
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Re: ACCCON TST

Post by jgharston » Thu Oct 31, 2019 6:18 pm

My *MDUMP command will page out the I/O area, and confirms that all three pages are paged out.
Image1.gif

Code: Select all

$ bbcbasic
PDP11 BBC BASIC IV Version 0.25
(C) Copyright J.G.Harston 1989,2005-2015
>_

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jgharston
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Re: ACCCON TST

Post by jgharston » Thu Oct 31, 2019 6:21 pm

Pernod wrote:
Thu Oct 31, 2019 1:17 pm
tom_seddon wrote:
Thu Oct 31, 2019 1:03 pm
MOS 3.50 has code in these pages.
I never noticed that before, but would suggest all 3 pages are paged out. Any idea what the code there does?
It's part of the RESET startup code, clears memory, initialises hardware, sets up default vectors, copies default font, etc. Stuff that's only done once.

Code: Select all

$ bbcbasic
PDP11 BBC BASIC IV Version 0.25
(C) Copyright J.G.Harston 1989,2005-2015
>_

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Pernod
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Re: ACCCON TST

Post by Pernod » Fri Nov 01, 2019 11:32 am

jgharston wrote:
Thu Oct 31, 2019 6:18 pm
My *MDUMP command will page out the I/O area, and confirms that all three pages are paged out.
Thanks for the confirmation, and code details.
- Nigel

BBC Model B: ATPL Sidewise, Acorn Speech, 2xWatford Floppy Drives, AMX Mouse, Viglen case, BeebZIF, etc.

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