Datasheet

TC1232
DS21370D-page 8 Preliminary  2002-2012 Microchip Technology Inc.
4.2 Push Button Reset Input
The debounced manual reset input (PB RST) manually
forces the reset outputs into their active states.
Figure 4-5 shows a block diagram for using the
TC1232 with a push button switch.
Once PB RST
has been low for a time t
PBD
(the push-
button delay time), the reset outputs go active. The
reset outputs remain in their active states for a
minimum of 250 ms after PB RST
rises above V
IH
.
Figure 4-6 shows a waveform for the push button
switch input and the reset pins output.
A mechanical push button or active logic signal can
drive the PB RST
input. The debounced input ignores
input pulses less than 1 ms and recognizes pulses of
20 ms or greater. No external pull-up resistor is
required
because the PB RST input has an internal
pull-up to
V
CC
of approximately 100 µA.
FIGURE 4-5: Push Button Reset and
Watchdog Timer.
FIGURE 4-6: Push Button Reset –
PB RST
Input.
V
CC
TOL
PB RST
GND
RST
ST
I/O
Reset
+5V
TC1232
TD
Microprocessor
RST
V
IL
t
PB
RST
t
PBD
V
IH
t
RST
PB RST
The debounced PB RST input ignores input pulses less
than 1 ms and is designed to recognize pulses of
20 ms or greater.