W77IE58_06 Datasheet, PDF (68/82 Pages) Winbond – 8-BIT MICROCONTROLLER

W77IE58/W77I058A
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
MOV
NOP
SETB
TA, #0AAh
TA, #055h
EWT
3 M/C
3 M/C
1 M/C
2 M/C
Example 3: Valid access
MOV
MOV
ORL
TA,#0AAh
3M/C
TA,#055h
3M/C
WDCON, #00000010B 3M/C
Example 4: Invalid access
MOV
MOV
NOP
NOP
CLR
TA, #0AAh
TA, #055h
POR
3 M/C
3 M/C
1 M/C
1 M/C
2 M/C
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 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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