Difference between revisions of "OSWORD &06"

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(Added mem_call.)
m (See Also)
 
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By copying code to the I/O processor and the I/O processor's USERV you can
 
By copying code to the I/O processor and the I/O processor's USERV you can
call an arbitary address in the I/O processor.
+
call an arbitary address in the I/O processor. These routines can be used if
 +
you know your program has complete control of USERV and does not have to
 +
restore it, or restores it elsewhere.
  
   DEFPROCmem_call(io%,A$):LOCAL old%
+
   DEFPROCio_call(io%,A$)
   !X%=&200:REPEAT
+
   !X%=&200:A%=6:REPEAT
    A%=5:CALL&FFF1:old%=256*X%?4+old%DIV256
+
     X%?4=io%:CALL&FFF1
     A%=6:X%?4=io%:CALL&FFF1:io%=io%DIV256
+
    io%=io%DIV256:?X%=?X%+1
    ?X%=?X%+1
 
 
   UNTIL ?X%=2
 
   UNTIL ?X%=2
 
   OSCLI "LINE "+A$
 
   OSCLI "LINE "+A$
   !X%=&200:REPEAT
+
   ENDPROC
    X%?4=old%:CALL&FFF1:old%=old%DIV256
 
    ?X%=?X%+1
 
  UNTIL ?X%=2
 
  =B%
 
 
   :
 
   :
   DEFFNmem_call(io%,B%,C%):LOCAL old%
+
   DEFFNio_call(io%,B%,C%)
   !X%=&200:REPEAT
+
   !X%=&200:A%=6:REPEAT
    A%=5:CALL&FFF1:old%=256*X%?4+old%DIV256
+
     X%?4=io%:CALL&FFF1
     A%=6:X%?4=io%:CALL&FFF1:io%=io%DIV256
+
    io%=io%DIV256:?X%=?X%+1
    ?X%=?X%+1
 
 
   UNTIL ?X%=2
 
   UNTIL ?X%=2
   B%=FNbyte(136,B%,C%)
+
   =FNbyte(136,B%,C%)
  !X%=&200:REPEAT
 
    X%?4=old%:CALL&FFF1:old%=old%DIV256
 
    ?X%=?X%+1
 
  UNTIL ?X%=2
 
  =B%
 
 
   DEFFNbyte(A%,X%,Y%)=((USR&FFF4)AND&FF00)DIV256
 
   DEFFNbyte(A%,X%,Y%)=((USR&FFF4)AND&FF00)DIV256
  
<code>PROCmem_call(address,"string")</code> will call ''address'', entering
+
<code>PROCio_call(address,"string")</code> will call ''address'', entering
 
with A=0 and XY pointing to ''string''. For example,
 
with A=0 and XY pointing to ''string''. For example,
<code>PROCmem_call(&FFF7,"HELP")</code> calls OSCLI in the I/O processor.
+
<code>PROCio_call(&FFF7,"HELP")</code> calls OSCLI in the I/O processor.
  
<code>result=FNmem_call(address,param1,param2)</code> will call ''address'',
+
<code>result=FNio_call(address,param1,param2)</code> will call ''address'',
 
entering with A=1, X=param1 and Y=param2, and will return the result in XY.
 
entering with A=1, X=param1 and Y=param2, and will return the result in XY.
For example, <code>result=FNmem_call(&FFE7,0,0)</code> will call OSNEWL in
+
For example, <code>result=FNio_call(&FFE7,0,0)</code> will call OSNEWL in
 
the I/O processor.
 
the I/O processor.
 
You should be careful if the called code generate an error as then USERV
 
will not be restored to its previous value.
 
  
 
==Implementations==
 
==Implementations==

Latest revision as of 20:30, 22 January 2021

OSWORD &06 (6) - Write I/O processor memory (Acorn MOS 1.00 and later)

 On entry:
   XY!0=address to write to
   XY?4=byte to be written.

Some systems recognise screen memory at &FFFExxxx and sideways ROMs at &FFrr8000-&FFrrBFFF.

Coding

The following routines can be used to copy data to and from I/O memory regardless of the location of the calling program. It requires X%=>5-byte control block, Y%=X%DIV256.

 DEFPROCmem_rd(io%,mem%,num%)
 A%=5:REPEAT
   !X%=io%:CALL&FFF1:?mem%=X%?4
   io%=io%+1:mem%=mem%+1:num%=num%-1
 UNTILnum%<1:ENDPROC
 :
 DEFPROCmem_wr(io%,mem%,num%)
 A%=6:REPEAT
   !X%=io%:X%?4=?mem%:CALL&FFF1
   io%=io%+1:mem%=mem%+1:num%=num%-1
 UNTILnum%<1:ENDPROC
 
 REM To read a single byte:
 !X%=addr:A%=5:CALL&FFF1:byte=X%?4
 :
 REM To write a single byte
 X%?4=byte:!X%=addr:A%=6:CALL&FFF1

By copying code to the I/O processor and the I/O processor's USERV you can call an arbitary address in the I/O processor. These routines can be used if you know your program has complete control of USERV and does not have to restore it, or restores it elsewhere.

 DEFPROCio_call(io%,A$)
 !X%=&200:A%=6:REPEAT
   X%?4=io%:CALL&FFF1
   io%=io%DIV256:?X%=?X%+1
 UNTIL ?X%=2
 OSCLI "LINE "+A$
 ENDPROC
 :
 DEFFNio_call(io%,B%,C%)
 !X%=&200:A%=6:REPEAT
   X%?4=io%:CALL&FFF1
   io%=io%DIV256:?X%=?X%+1
 UNTIL ?X%=2
 =FNbyte(136,B%,C%)
 DEFFNbyte(A%,X%,Y%)=((USR&FFF4)AND&FF00)DIV256

PROCio_call(address,"string") will call address, entering with A=0 and XY pointing to string. For example, PROCio_call(&FFF7,"HELP") calls OSCLI in the I/O processor.

result=FNio_call(address,param1,param2) will call address, entering with A=1, X=param1 and Y=param2, and will return the result in XY. For example, result=FNio_call(&FFE7,0,0) will call OSNEWL in the I/O processor.

Implementations

All 8-bit Acorn systems write to whichever ROM/RAM is paged in. All except the BBC B+ write to main memory. The B+ recognises &FFFExxxx to write to the shadow screen memory, otherwise it writes to main memory. It is possible to write a modified Tube Host that intercepts OSWORD 5 and 6 to access extended memory, but most programs rely on adding an extra OSWORD call.

See Also

Jgharston 23:54, 30 October 2011 (UTC) Jgharston (talk) 04:28, 29 March 2015 (UTC) Jgharston (talk) 14:02, 31 January 2016 (UTC)