W77E532 Datasheet, PDF (66/86 Pages) Winbond – 8 BIT MICROCONTROLLER

W77E532/W77E532A
Examples of Timed Assessing are shown below.
Example 1: Valid access
MOV TA, #0Aah 3 M/C
MOV TA, #055h 3 M/C
MOV WDCON, #00h 3 M/C
Note: M/C = Machine Cycles
Example 2: Valid access
MOV TA, #0Aah 3 M/C
MOV TA, #055h 3 M/C
NOP
1 M/C
SETB EWT
2 M/C
Example 3: Valid access
MOV TA, #0Aah 3 M/C
MOV TA, #055h 3 M/C
ORL WDCON, #00000010B
3M/C
Example 4: Invalid access
MOV TA, #0Aah 3 M/C
MOV TA, #055h 3 M/C
NOP
1 M/C
NOP
1 M/C
CLR POR
2 M/C
Example 5: Invalid Access
MOV TA, #0Aah 3 M/C
NOP
1 M/C
MOV TA, #055h 3 M/C
SETB EWT
2 M/C
In the first two examples, the writing to the protected bits is done before the 3 machine cycle window
closes. In Example 3, 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 4, 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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Publication Release Date: June 30, 2009
Revision A10