ST10F167 datasheet(29/69 Pages) STMICROELECTRONICS

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ST10F167

WATCHDOG TIMER

The Watchdog Timer is a fail-safe mechanism. It

limits the maximum malfunction time of the con-

troller

The Watchdog Timer is always enabled after a re-

set of the chip, and can only be disabled in the

time interval until the EINIT (end of initialization)

instruction has been executed. In this way the

chip’s start-up procedure is always monitored. The

software must be designed to service the Watch-

dog Timer before it overflows. If, due to hardware

or software related failures, the software fails to do

so, the Watchdog Timer overflows and generates

an internal hardware reset and pulls the RSTOUT

pin low in order to allow external hardware compo-

nents to be reset.

The Watchdog Timer is a 16-bit timer, clocked with

the system clock divided either by 2 or by 128. The

high byte of the Watchdog Timer register can be

set to a pre-specified reload value (stored in

WDTREL) in order to allow further variation of the

monitored time interval. Each time it is serviced by

the application software, the high byte of the

Watchdog Timer is reloaded. Therefore, time inter-

vals between 25

µs and 420ms can be monitored

(@ 20 MHz). The default Watchdog Timer interval

after reset is 6.55 ms (@ 20 MHz).

A/D CONVERTER

A 10-bit A/D converter with 16 multiplexed input

channels and a sample and hold circuit has been

integrated on-chip for

analog signal measure-

ment. It uses a successive approximation method.

The sample time (for loading the capacitors) and

conversion time is programmable and can be

modified for the external circuitry.

Overrun error detection/protection is provided for

the conversion result register (ADDAT). When the

result of a previous conversion has not been read

from the result register at the time the next conver-

sion is complete, either an interrupt request is gen-

erated, or the next conversion is suspended, until

the previous result has been read.

For applications which require less than 16 analog

input channels, the remaining channel inputs can

be used as digital input port pins.

The A/D converter of the ST10F167 supports four

different conversion modes. In the standard Single

Channel conversion mode, the analog level on a

specified channel is sampled once and converted

to a digital result. In the Single Channel Continu-

ous mode, the analog level on a specified channel

is repeatedly sampled and converted without soft-

ware intervention. In the Auto Scan mode, the an-

alog levels on a prespecified number of channels

are sequentially sampled and converted. In the

Auto Scan Continuous mode, the number of pre-

specified channels is repeatedly sampled and con-

verted. In addition, the conversion of a specific

channel can be inserted (injected) into a running

sequence without disturbing this sequence. This is

called Channel Injection Mode.

The Peripheral Event Controller (PEC) may be

used to automatically store the conversion results

into a table in memory for later evaluation, without

the overhead of interrupt routines for each data

transfer.

After each reset and also during normal operation,

the ADC automatically performs calibration cycles.

This automatic self-calibration constantly adjusts

the converter to the changing operating conditions

(e.g. temperature) and compensates process vari-

ations.

These calibration cycles are part of the conversion

cycle. They do not affect the normal operation of

the A/D converter.

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