at90ls4433 ATMEL Corporation, at90ls4433 Datasheet - Page 23

• Manufacturer Part Number: at90ls4433
• Description: At90s4433 8-bit Avr Microcontroller With 4k Bytes Of In-system Programmable Flash
• Manufacturer: ATMEL Corporation

Power-on Reset
1042H–AVR–04/03
Table 5. Reset Delay Selections
Note:
This table shows the Start-up times from Reset. From sleep, only the clock counting part
of the Start-up time is used. The Watchdog Oscillator is used for timing the Real Time
part of the Start-up time. The number WDT Oscillator cycles used for each time-out is
shown in Table 6.
Table 6. Number of Watchdog Oscillator Cycles
The frequency of the Watchdog Oscillator is voltage dependent, as shown in the Electri-
cal Characteristics section.
A Power-on Reset (POR) pulse is generated by an On-chip Detection circuit. The detec-
tion level is nominally 2.2V. The POR is activated whenever V
level. The POR circuit can be used to trigger the Start-up Reset, as well as detect a fail-
ure in supply voltage.
The Power-on Reset (POR) circuit ensures that the device is Reset from Power-on.
Reaching the Power-on Reset threshold voltage invokes a delay counter, which deter-
mines the delay, for which the device is kept in RESET after V
period of the delay counter is a combination of Internal RC Oscillator cycles and Exter-
nal Oscillator cycles, and it can be defined by the user through the CKSEL Fuses. The
eight different selections for the delay period are presented in Table 5. The RESET sig-
nal is activated again, without any delay, when the V
level.
Time-out
4.0 ms (at V
64 ms (at V
CKSEL
[2:0]
000
001
010
011
100
101
110
111
1. Or external Power-on Reset.
t
CC
256 ms + 16K CK
TOUT
CC
16 ms + 16K CK
256 ms + 1K CK
Start-up Time,
16 ms + 1K CK
16 ms + 6 CK
= 5.0V)
= 5.0V)
at V
16K CK
1K CK
6 CK
CC
= 2.7V
t
TOUT
64 ms + 16K CK
Start-up Time,
4 ms + 16K CK
64 ms + 1K CK
4 ms + 1K CK
4 ms + 6 CK
at V
16K CK
1K CK
6 CK
CC
= 5.0V
Recommended Usage
External Clock, slowly rising power
External Clock, BOD enabled
Crystal Oscillator
Crystal Oscillator, fast rising power
Crystal Oscillator, BOD enabled
Ceramic Resonator
Ceramic Resonator, fast rising power
Ceramic Resonator, BOD enabled
CC
decreases to below detection
Number of Cycles
AT90S/LS4433
CC
64K
CC
is below the detection
4K
rise. The Time-out
(1)
(1)
(1)
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