W79E201 Datasheet, PDF (64/87 Pages) Winbond – 8-BIT MICROCONTROLLER

W79E201
NOP
NOP
CLR
POR
Example 5: Invalid Access
MOV TA, #0AAh
NOP
MOV TA, #055h
SETB EWT
1 M/C
1 M/C
2 M/C
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.
17. H/W REBOOT MODE (BOOT FROM 4K BYTES OF LD FLASH EPROM)
The W79E201 boots from AP Flash EPROM program (16K bytes) by default at the external reset. On
some occasions, user can force W79E201 to boot from the LD Flash EPROM program (4K bytes) at
the external reset. The set for this special mode is as follow. It is necessary to add 10K resistor on
P4.0 pins.
Reboot Mode
OPTION BITS
RST P4.0
MODE
Bit3 L
H
L
REBOOT
The Reset Timing For Entering
REBOOT Mode
P4.0
Hi-Z
RST
20 US
10 mS
Notes:
1: In application system design, user must take care the P4.0, ALE, /EA and /PSEN pin value at reset to avoid W79E201
entering the programming mode or REBOOT mode in normal operation.
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