ST10F268 datasheet(36/74 Pages) STMICROELECTRONICS

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ST10F168

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15 - CAN MODULE

The integrated CAN module completely handles

the autonomous transmission and the reception of

CAN frames according to the CAN specification

V2.0 part B (active). 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 mes-

sage objects can be updated independently from

other objects and are equipped for the maximum

message length of 8 Bytes.

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.

16 - 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 procedure is always

monitored. The software must be designed to ser-

vice the watchdog timer before it overflows. If, due

to hardware or software related failures, the soft-

ware fails to do so, the watchdog timer overflows

and generates an internal 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 20 shows the watchdog time range for

25MHz CPU clock.

Table 20 : Watchdog time range (25MHz 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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