Date: 11/29/04

SP690A/692A Low Power Microprocessor Supervisory with Battery Switch-Over

© Copyright 2004 Sipex Corporation

13

Interfacing to Microprocessors with

Bidirectional Reset Pins

Microprocessors with bidirectional reset pins,

such as the Motorola 68HC11 series, can con-

tend with this series' RESET output. If, for

example, the RESET output is driven high and

the

µP wants to pull it low, indeterminate logic

levels may result. To correct this, connect a

4.7K

Ω resistor between the RESET output and

the

µP reset I/O, as in Figure 20. Buffer the

RESET output to other system components.

Figure 19. Monitoring a Negative Voltage

Figure 20. Interfacing to Microprocessors with

Bidirectional RESET I/O

PFI

PFO

+5V

GND

PFO

V-

+5V

0V

5.0 - 1.25

V-

=

+5V

GND

+5V

GND

RESET

RESET

4.7KΩ

µP

Buffered RESET connects to System Components