at83c5122 ATMEL Corporation, at83c5122 Datasheet - Page 173

• Manufacturer Part Number: at83c5122
• Description: At83c5123 C51 Microcontroller With Usb And Smart Card Reader Interfaces
• Manufacturer: ATMEL Corporation

Power On Reset (POR)
Power Fail Detector
(PFD)
4202E–SCR–06/06
The role of the POR is to monitor the power supply rise of the microcontroller core and
release the internal reset only when the internal voltage exceeds the VPFDP threshold
from which the microcontroller core is stable (see Figure 102). This feature replaces the
external reset function and therefore avoid the use of external components on the reset
pin.
The role of the PFD is to monitor the power supply falls during a steady state condition
in order to suspend the microcontroller and peripherals activity as soon as the power
supply drops below the VPFDM threshold from which the microcontroller’s core might
become instable (see Figure 102). The PDF suspends the microcontroller’s activity by
holding the microcontroller under a reset state to avoid an unpredictable behaviour.
A filter prevents the system from reseting when glitches lower than 50 ns duration are
carried on Vcore. See Figure 102 and Figure 103 on page 174.
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