W77E532_07 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.
- 66 -
Publication Release Date: November 19, 2007
Revision A9