Difference between revisions of "OSBYTE &A2"
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with OSBYTE &A2. See also [[Talk:OSBYTE &A2]]. | with OSBYTE &A2. See also [[Talk:OSBYTE &A2]]. | ||
| − | ==Write | + | ==Write non-volatile memory== |
On entry: | On entry: | ||
| − | X= | + | X=offset to byte to write |
Y=byte to write | Y=byte to write | ||
On exit: | On exit: | ||
| − | + | If unsupported: X=&FF | |
| + | Y=preserved | ||
| + | If offset within non-volative memory exists: | ||
| + | X=absolute offset within memory | ||
| + | Y=preserved | ||
| + | If offset within non-volatile memory does not exist (past last location): | ||
| + | X=preserved | ||
| + | Y=preserved | ||
| − | OSBYTE &A2 | + | OSBYTE &A2 writes a byte to non-volatile memory used to store configuration data. |
| − | 50 locations but implementations can have more. The Master 128 uses 50 bytes | + | There are typically 50 locations but implementations can have more. The Master 128 |
| − | of | + | uses 50 bytes of non-volatile CMOS RAM, the Master Compact uses a 128-byte or a |
| − | the Master Extension ROM for the BBC B uses a block of memory or a file on disk. | + | 256-byte EEPROM, the Master Extension ROM for the BBC B uses a block of memory or |
| + | a file on disk. | ||
Location zero holds the local station number and is protected from being written | Location zero holds the local station number and is protected from being written | ||
with OSBYTE &A2. It can only be changed with a utility such as <tt>'''*SetStation'''</tt>. | with OSBYTE &A2. It can only be changed with a utility such as <tt>'''*SetStation'''</tt>. | ||
| − | Some implementations of | + | Some implementations of non-volatile memory have a limited write-cycle time, so |
it is best to only write a value if it is not already the same. The following | it is best to only write a value if it is not already the same. The following | ||
code will write a block of configuration data: | code will write a block of configuration data: | ||
| Line 30: | Line 38: | ||
REM mem%=block of configuration data | REM mem%=block of configuration data | ||
FOR X%=1 TO max% | FOR X%=1 TO max% | ||
| − | A%=161:Y%=((USR&FFF4)AND&FF0000) | + | A%=161:Y%=((USR&FFF4)AND&FF0000)DIV65536 |
IF mem%?X%<>Y% THEN Y%=mem%?X%:A%=162:CALL &FFF4 | IF mem%?X%<>Y% THEN Y%=mem%?X%:A%=162:CALL &FFF4 | ||
NEXT X% | NEXT X% | ||
==See Also== | ==See Also== | ||
| − | * Read | + | * Read non-volatile memory [[OSBYTE &A1]] |
* [[CMOS configuration RAM allocation]] | * [[CMOS configuration RAM allocation]] | ||
* [http://mdfs.net/Docs/Comp/BBC/Osbyte80 mdfs.net OSBYTE list] | * [http://mdfs.net/Docs/Comp/BBC/Osbyte80 mdfs.net OSBYTE list] | ||
[[User:Jgharston|Jgharston]] 16:06, 31 October 2010 (UTC) | [[User:Jgharston|Jgharston]] 16:06, 31 October 2010 (UTC) | ||
Revision as of 22:53, 26 August 2024
Enable/Disable GXR
On entry: X=0 Disable GXR (version 1.xx), Enable GXR (version 2.xx) X=128 Enable GXR (version 1.xx), Disable GXR (version 2.xx)
The Graphics Extension ROM for the BBC B and BBC B+ can be enabled and disabled with OSBYTE &A2. See also Talk:OSBYTE &A2.
Write non-volatile memory
On entry:
X=offset to byte to write
Y=byte to write
On exit:
If unsupported: X=&FF
Y=preserved
If offset within non-volative memory exists:
X=absolute offset within memory
Y=preserved
If offset within non-volatile memory does not exist (past last location):
X=preserved
Y=preserved
OSBYTE &A2 writes a byte to non-volatile memory used to store configuration data. There are typically 50 locations but implementations can have more. The Master 128 uses 50 bytes of non-volatile CMOS RAM, the Master Compact uses a 128-byte or a 256-byte EEPROM, the Master Extension ROM for the BBC B uses a block of memory or a file on disk.
Location zero holds the local station number and is protected from being written with OSBYTE &A2. It can only be changed with a utility such as *SetStation.
Some implementations of non-volatile memory have a limited write-cycle time, so it is best to only write a value if it is not already the same. The following code will write a block of configuration data:
REM max%=number of locations -1 REM mem%=block of configuration data FOR X%=1 TO max% A%=161:Y%=((USR&FFF4)AND&FF0000)DIV65536 IF mem%?X%<>Y% THEN Y%=mem%?X%:A%=162:CALL &FFF4 NEXT X%
See Also
- Read non-volatile memory OSBYTE &A1
- CMOS configuration RAM allocation
- mdfs.net OSBYTE list
Jgharston 16:06, 31 October 2010 (UTC)
