AT89C5122 ATMEL [ATMEL Corporation], AT89C5122 Datasheet - Page 172

• Manufacturer Part Number: AT89C5122
• Description: MICROCONTROLLER WITH USB AND SMART CARD READER INTERFACES
• Manufacturer: ATMEL [ATMEL Corporation]

Microcontroller Reset
Introduction
172
AT8xC5122/23
The internal reset is used to start up (cold reset) or to re-start (warm reset) the micro-
controller activity. When the reset is applied (active state), all internal registers are
initialized so that the microcontroller starts from a known and clean state for the program
always runs as expected.
The reset is released (inactive state) when the following conditions are internally met :
If one of the above conditions is not met the microcontroller is not correctly reset and
might not work properly.
The internal reset comes from four different sources :
Figure 101. Reset bock diagram
RST
Vcc
–
–
–
–
–
–
–
The power supply has reatched a minimum level which garantees that the
microcontroller works properly
The on-chip oscillator has reached a minimum oscillation level which
ensures a good noise to signal ratio and a correct internal duty cycle
the active state duration is at least two machine cycles.
Reset pin
Power On Reset (POR)
Power Fail Detector (PFD)
Hardware Watch-Dog Timer (WDT)
3.3V Internal
Digital Regulator
POR
Watch Dog
Timer
PFD
Core
C51
Microcontroller
Internal Reset
4202D–SCR–06/05
VCore