W79E632A Datasheet, PDF (60/79 Pages) Winbond – 8-BIT MICROCONTROLLER

W79E632A/W79L632A
Example 4: Invalid access
MOV
MOV
NOP
NOP
CLR
TA, #0AAh
TA, #055h
POR
Example 5: Invalid Access
MOV TA, #0AAh
NOP
MOV TA, #055h
SETB EWT
3 M/C
3 M/C
1 M/C
1 M/C
2 M/C
3 M/C
1 M/C
3 M/C
2 M/C
In the first three examples, the writing to the protected bits is done before the 3 machine cycle window
closes. In Example 4, however, the writing to the protected bit occurs after the window has closed, and
so there is effectively no change in the status of the protected bit. In Example 5, the second write to TA
occurs 4 machine cycles after the first write, therefore the timed access window in not opened at all, and
the write to the protected bit fails.
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