Date : Mon, 09 Sep 2002 10:10:36 +0100
From : owner-bbc-micro@...
Subject: Regaining disc drive memory work space
-----Original Message-----
From: Christopher Dewhurst Clerical Assistant SS
Sent: 09 September 2002 09:44
To: 'james watson'
Subject: RE: [BBC-Micro] Regaining disc drive memory work space
Hi Folks
This can also be done faster in machine code (doing this from memory, let me
know if I've missed summat):
FOR N%=0 TO 2 STEP 2
P%=&900
[OPT N%
\ Set up pointers
\ &70/71 = &1900 (source address)
\ &72/73 = &E00 (destination address)
LDY #0:STY &70:STY &72
LDA #&19:STA &71
LDA #&0E:STA &73
LDX #&20 \number of pages to be moved e.g. &20 for program length &2000
.loop LDA (&70),Y
STA (&72),Y
INY:BNE loop
INC &71:INC &73
DEX:BNE loop
RTS
]NEXT
Include the above lines in a loader program; it could be assembled in a
procedure, for example. You would still have to do something like CALL &900
:PAGE=&E00:RUN in Basic - it *could* be done in machine code but not very
easily - or else subsitute RTS for CALL &xxxx where xxxx is the original
execution address of the machine code. Note that it downloads round pages of
code, not a problem so long as you set the X register to the next nearest
number of pages, e.g. &11 for a program that is &1021 bytes long.
Regards
Christopher.
-----Original Message-----
From: james watson [mailto:james@...]
Sent: 06 September 2002 20:29
To: bbc-micro@...
Subject: [BBC-Micro] Regaining disc drive memory work space
When using a disc drive on a BBC micro, Page is moved from &E00 to &1900 to
create memory work space for the disc drive. Is possible to regain the disc
drive work space once the program has loaded. I.e resetting page back to
&E00. Can anybody give an example of various techniques on how to achieve
this.
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