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| | X=offset within page &FE and Y=byte to write | | X=offset within page &FE and Y=byte to write |
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| − | ;Warning
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| − | Acorn MOS 1.20 writes the byte using <code>STA &FE00,X</code> (at address &EAFF). As it is an indexed-addressing instruction, the 6502 CPU performs a dummy read immediately before the write. Some hardware, though not all, may operate inappropriately due to the dummy read: outputs could momentarily be set to the wrong level, or an interrupt condition could be cleared and lost. Review the datasheet for the hardware being accessed to see whether it will be adversely affected.
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| − | The safe alternative is to call [[OSWORD &06]] with !XY = &FFFFFExx and XY?4 = byte to write.
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| | ==See Also== | | ==See Also== |
Revision as of 18:32, 28 August 2015
OSBYTE &97 (151) - Write SHELIA
X=offset within page &FE and Y=byte to write
See Also
Jgharston 22:08, 26 May 2009 (UTC)
