3

Number

Pins

Type

Description

8WDO

Digital Output

Watchdog output. Active low push-pull output driver. This pin is usually connected

to a non-maskable interrupt input of a microprocessor. On power up, WDO responds

is reached. At that point, WDO is raised high. The internal watchdog timer is activated

after RESET is released. If there is no activity on WDI input, WDO goes low after

the watchdog timer times out, which is typically after 1.6sec. Any activity on WDI

will force WDO output to go high and the watchdog timer will be activated. If WDI

is floating or connected to a high impedance buffer output, the timer is kept in a reset

state and WDO stays high. When VDD drops below 3.08V, WDO goes low regardless

of whether the watchdog timer has timed out or not. RESET goes low simultaneously

which prevents an interrupt.

If WDI input is left unconnected, WDO can be used as a low line output. Since a

below 3.08V, thus, functioning as a low line output. (Figure 4.)

Figure 2. UT01VS33L Pin Configuration

MR

VDD

GND

PFI

WDO

RESET

WDI

PFO

1

2

3

4

8

7

6

5

UT01VS33L