W79E217A Datasheet, PDF (183/207 Pages) Winbond – 8-bit Microcontroller

Preliminary W79E217A Data Sheet
Example 5: Invalid Access
MOV TA, #0AAh
NOP
MOV TA, #055h
SETB EWT
3 M/C
1 M/C
3 M/C
2 M/C
In the first three examples, the protected bits are written before the window closes. In Example 4,
however, the write occurs after the window has closed, so there is no change in the protected bit. In
Example 5, the second write to TA occurs four machine cycles after the first write, so the timed access
window in not opened at all, and the write to the protected bit fails.
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Publication Release Date: December 14, 2007
Revision A3.0