STM706 datasheet(6/27 Pages) STMICROELECTRONICS

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STM705/706/707/708/813L

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Pin Descriptions

MR.A logic low on MR asserts the reset output.

Reset remains asserted as long as MR is low and

for trec after MR returns high. This active-low input

has an internal pull-up. It can be driven from a TTL

or CMOS logic line, or shorted to ground with a

switch. Leave open if unused.

WDI. If WDI remains high or low for 1.6sec, the in-

ternal watchdog timer runs out and reset (or WDO)

is triggered. The internal watchdog timer clears

while reset is asserted or when WDI sees a rising

or falling edge.

The watchdog function can be disabled by allow-

ing the WDI pin to float.

WDO.It goes low when a transition does not oc-

cur on WDI within 1.6sec, and remains low until a

transition occurs on WDI (indicating the watchdog

interrupt has been serviced). WDO also goes low

when VCC falls below the reset threshold; howev-

er, unlike the reset output, WDO goes high as

soon as VCC exceeds the reset threshold.

Note: For those devices with a WDO output, a

watchdog timeout will not trigger reset unless

WDO is connected to MR.

RST.Pulses low when triggered, and stays low

whenever VCC is below the reset threshold or

when MR is a logic low. It remains low for trec after

either VCC rises above the reset threshold, or MR

goes from low to high.

RST. Goes high with triggered, and stays high

whenever VCC is above the reset threshold or

when MR is a logic high. It stays high for trec after

either VCC falls below the reset threshold, or MR

goes from high to low.

PFI. When PFI is less than VPFI, PFO goes low;

otherwise, PFO remains high. Connect to ground

if unused.

PFO.When PFI is less than VPFI, PFO goes low;

otherwise, PFO remains high. Leave open if un-

used.

Table 3. Pin Description

Name

Function

STM813L

STM707

STM708

STM705

STM706

111

Push-button Reset Input

–

WDI

Watchdog Input

8–8

WDO

Watchdog Output

–77

RST

Active-Low Reset Output

–

RST

Active-High Reset Output

222

VCC

Supply Voltage

PFI

PFI Power-fail Input

555

PFO

PFO Power-fail Output

333

VSS

Ground

–

No Connect

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