at90ls8535-8mi ATMEL Corporation, at90ls8535-8mi Datasheet - Page 22

• Manufacturer Part Number: at90ls8535-8mi
• Description: 8-bit Microcontroller With 8k Bytes In-system Programmable Flash
• Manufacturer: ATMEL Corporation

Power-on Reset
22
AT90S/LS8535
placed at these locations. The circuit diagram in Figure 23 shows the reset logic. Table 3
defines the timing and electrical parameters of the reset circuitry.
Figure 23. Reset Logic
Table 3. Reset Characteristics (V
Note:
Table 4. Number of Watchdog Oscillator Cycles
A Power-on Reset (POR) circuit ensures that the device is reset from power-on. As
shown in Figure 23, an internal timer clocked from the Watchdog Timer oscillator pre-
vents the MCU from starting until after a certain period after V
on Threshold voltage (V
The user can select the start-up time according to typical oscillator start-up time. The
number of WDT oscillator cycles is shown in Table 4. The frequency of the Watchdog
oscillator is voltage-dependent as shown in “Typical Characteristics” on page 107.
If the built-in start-up delay is sufficient, RESET can be connected to V
an external pull-up resistor. By holding the pin low for a period after V
applied, the Power-on Reset period can be extended. Refer to Figure 25 for a timing
example of this.
V
FSTRT
Programmed
Unprogrammed
Symbol
POT
t
t
V
TOUT
TOUT
RST
(1)
1. The Power-on Reset will not work unless the supply voltage has been below V
(falling).
Parameter
Power-on Reset Threshold (rising)
Power-on Reset Threshold (falling)
Reset Delay Time-out Period
FSTRT Unprogrammed
Reset Delay Time-out Period
FSTRT Programmed
RESET Pin Threshold Voltage
POT
), regardless of the V
Time-out at V
CC
16.0 ms
1.1 ms
= 5.0V)
CC
= 5V
CC
rise time (see Figure 24).
11.0
Min
1.0
0.4
1.0
Number of WDT Cycles
CC
0.6 V
16.0
Typ
1.4
0.6
1.1
has reached the Power-
CC
16K
1K
CC
Max
21.0
1.8
0.8
1.2
directly or via
CC
has been
1041H–11/01
Units
ms
ms
V
V
V
POT