Difference between revisions of "OSWORD &06"
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[[Category:OSWORD]][[Category:Second Processors]]__NOTOC__ | [[Category:OSWORD]][[Category:Second Processors]]__NOTOC__ | ||
| − | + | {{PageTitle|OSWORD &06 (6): Write I/O processor memory}} | |
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On entry: | On entry: | ||
XY!0=address to write to | XY!0=address to write to | ||
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Some systems recognise screen memory at &FFFExxxx and sideways ROMs at | Some systems recognise screen memory at &FFFExxxx and sideways ROMs at | ||
| − | &FFrr8000-&FFrrBFFF. | + | &FFrr8000 - &FFrrBFFF. |
==Coding== | ==Coding== | ||
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==Implementations== | ==Implementations== | ||
| + | Implemented in Acorn MOS 1.00 and later. | ||
| + | |||
All 8-bit Acorn systems write to whichever ROM/RAM is paged in. All except | 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 | the BBC B+ write to main memory. The B+ recognises &FFFExxxx to write to the | ||
Latest revision as of 17:50, 7 January 2023
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
Implemented in Acorn MOS 1.00 and later.
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
- OSWORD &05
- OSWORD &FA
- OSWORD &FF
- http://mdfs.net/Docs/Comp/BBC/Oswords
- MemIO library at http://mdfs.net/blib
Jgharston 23:54, 30 October 2011 (UTC) Jgharston (talk) 04:28, 29 March 2015 (UTC) Jgharston (talk) 14:02, 31 January 2016 (UTC)
