ST10 datasheet(26/65 Pages) STMICROELECTRONICS

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ST10C167

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XIV - CAN MODULE

The integrated CAN module handles the com-

pletely autonomous transmission and reception of

CAN frames in accordance with the CAN specifi-

cation V2.0 part B (active) i.e. the on-chip CAN

module can receive and transmit standard frames

with 11-bit identifiers as well as extended frames

with 29-bit identifiers.

The CAN module provides full CAN functionality

on up to 15 message objects. Message object 15

can be configured for basic CAN functionality.

Both modes provide separate masks for accep-

tance filtering, allowing a number of identifiers in

full CAN mode to be accepted and disregarding a

number of identifiers in basic CAN mode.

All message objects can be updated independent

from other objects and are equipped for the maxi-

mum message length of 8 Byte.

The bit timing is derived from the XCLK and is pro-

grammable up to a data rate of 1M Baud. The

CAN module uses two pins to interface to a bus

transceiver.

XV - WATCHDOG TIMER

The Watchdog Timer is a fail-safe mechanism

which prevents the microcontroller from malfunc-

tioning for long periods of time. The Watchdog

Timer is always enabled after a reset of the chip

and can only be disabled in the time interval until

the EINIT (end of initialization) instruction has

been executed. Therefore, the chip start-up pro-

cedure is always monitored. The software must

be designed to service the watchdog 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 inter-

nal hardware reset. It pulls the RSTOUT pin low in

order to allow external hardware components to

be reset.

The Watchdog Timer is 16-bit, clocked with the

system clock divided by 2 or 128. The high Byte of

the watchdog timer register can be set to a

pre-specified reload value (stored in WDTREL).

Each time it is serviced by the application soft-

ware, the high Byte of the watchdog timer is

reloaded.

For security, rewrite WDTCON each

time before the watchdog timer is serviced

Table 12 : Watchdog time range for 25MHz CPU clock

Reload value in WDTREL

Prescaler for fCPU

2 (WDTIN = ‘0’)

128 (WDTIN = ‘1’)

FFH

20.48

µs

1.31ms

00H

5.24ms

336ms

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