62
AT94KAL Series FPSLIC
Rev. 1138G–FPSLI–11/03
Note:
1. The Power-on Reset will not work unless the supply voltage has been below V
POT
(falling).
Power-on Reset
A Power-on Reset (POR) circuit ensures that the device is reset from power-on. As shown in
Figure 35, an internal timer clocked from the Watchdog Timer oscillator prevents the MCU
from starting until after a certain period after V
CC
has reached the Power-on Threshold voltage
– V
POT
, regardless of the V
CC
rise time (see Figure 36 and Figure 37).
Figure 36.
MCU Start-up, RESET Tied to V
CC
Figure 37.
Watchdog Reset during Operation
Table 16.
Reset Characteristics (V
CC
= 3.3V)
Symbol
Parameter
Minimum
Typical
Maximum
Units
V
POT(1)
Power-on Reset Threshold
(Rising)
1.0
1.4
1.8
V
Power-on Reset Threshold
(Falling)
0.4
0.6
0.8
V
V
RST
RESET Pin Threshold
Voltage
V
CC
/2
V
T
TOUT
Reset Delay Time-out Period
5
CPU
cycles
0.4
3.2
12.8
0.5
4.0
16.0
0.6
4.8
19.2
ms
V
CC
RESET
TIME-OUT
INTERNAL RESET
t
TOUT
V
POT
V
RST
RESET (HIGH)
RESET TIME-OUT
INTERNAL RESET
WDT TIME-OUT
t
TOUT
1 XTAL CYCLE
V
CC
(HIGH)