Datasheet

4
7764A–8051–11/07
Figure 1-3. Reset bock diagram
Watch Dog
RST
Internal Reset
Timer
Microcontroller
Vcc
C51
Core
POR
PFD
Table 1-2. Features descriptions
Feature Description Impact on RST pin
PFD
The role of the PFD is to monitor the power supply drops during a steady state
condition in order to suspend the microcontroller’s activity. When the PFD is
active, it holds the MCU under a reset state to prevent the MCU from having
unpredictable behaviour.
Optional feature
While the PFD is active, the reset pin
is driven by the PFD.
POR
The role of the POR is to monitor the rising of internal power supply of the
microcontroller core. It releases the internal reset only when the internal
voltage is enough for the core to operate.
Optional feature
- No external components or
superviser devices are needed to
drive the reset pin
- While the POR is active, the reset pin
is driven by the POR
- RST pin may be left unconnected
WDT
The WDT automatically resets the chip if the software fails to reset the WDT
before the selected time interval has elapsed.
Basic feature of C51 devices
While the WDT is active, the reset pin
is driven by the WDT.
Internal
Pull-up
Saves an external component No external pull-up needed