Date   : Tue, 25 Jul 2006 08:08:31 +0100 (BST)
From   : Steve Fewell <kranser@...>
Subject: Re: 6502 copros again

--- Jules Richardson <julesrichardsonuk@...>
wrote:

> 
> OK, I think the copro is working... at startup I get
> "Acorn TUBE 6502 64K". 
> System memory variables as follows:
> 
>              PAGE  HIMEM  TOP
> no copro:   6400  31744  6402
> with copro: 2048  32768  2050
> 
> .. can someone with a known-good copro confirm
> that's what they get too?

An additional system variable that is different for a
coprocessor is the Operating System High Order Address
(OSBYTE &82).
On a standard BBC B/Master it is as follows:
A% = &82 : P.~USR(&FFF4)
 B1FFFF82

The middle 4 digits (X and Y) are &FFFF giving the
standard high order address.

But on a co-processor, the value is as follows:
A% = &82 : P.~USR(&FFF4)
 33000082

The middle 4 digits (X and Y) are &0000 giving the
high order address on a coprocessor.

Is this what you get?



       
       
               
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