 2004 Microchip Technology Inc.

DS21877A-page 5

TC1272A

3.3

Controllers and Processors With

Bidirectional I/O Pins

Some microcontrollers have bidirectional reset pins.

Depending on the current drive capability of the

controller pin, an indeterminate logic level may result if

there is a logic conflict. This can be avoided by adding

a 4.7 k

Ω resistor in series with the output of the

TC1272A (Figure 3-3). If there are other components in

the system that require a reset signal, they should be

buffered so as not to load the reset line. If the other

components are required to follow the reset I/O of the

microcontroller, the buffer should be connected as

shown with the solid line.

FIGURE 3-3:

Interfacing the TC1272A to

a Bidirectional RESET I/O.

TC1272A

V

DD

RESET

GND

RESET

GND

Buffered RESET

To Other System

Components

4.7 k

Ω

Buffer

Micro-

TC1272A

RESET

GND

RESET

GND

Buffered RESET

To Other System

Components

4.7 k

Ω

Buffer

MCU