STM706P datasheet(6/26 Pages) STMICROELECTRONICS

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STM706T/S/R; STM706P; STM708T/S/R

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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 cannot be disabled by al-

lowing the WDI pin to float.

WDO. WDO goes low when a transition does not

occur on WDI within 1.6sec, and remains low until

a transition occurs on WDI (indicating the watch-

dog interrupt has been serviced). WDO also goes

low when VCC falls below the reset threshold; how-

ever, 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 for trec 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, the

watchdog triggers a reset, or MR goes from low to

high.

RST. Pulses high for trec when triggered, and

stays high whenever VCC is above the reset

threshold or when MR is a logic high. It remains

high for trec after either VCC falls below the reset

threshold, the watchdog triggers a reset, 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

STM706P

STM706T/S/R

STM708T/S/R

SO8

TSSOP8

SO8

TSSOP8

SO8

TSSOP8

131313

Push-button Reset Input

6868––

WDI

Watchdog Input

8282––

WDO

Watchdog Output

––7171

RST

Active-Low Reset Output

71––82

RST

Active-High Reset Output

242424

VCC

Supply Voltage

464646

PFI

PFI Power-fail Input

575757

PFO

PFO Power-fail Output

353535

VSS

Ground

––––68

No Connect

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