MC33389 Ver la hoja de datos (PDF) - Motorola => Freescale

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componentes Descripción

Fabricante

MC33389

System Basis Chip with Low Speed Fault Tolerant CAN

Motorola => Freescale 

MC33389

FreescalDeEVSICEeDmESiCcRoIPnTIOdNuctor, Inc.

SBC MODES

be taken into account by the SBC (except for the go to

Emergency mode).

Correspondence between SBC and CAN Transceiver Modes

The table here below gives the different possible CAN

transceiver modes versus SBC modes.

Table 14. CAN Modes Versus SBC Modes

In normal mode the SBC get the watchdog word from the

microcontroller via SPI. In case of a trigger time failure (no

trigger or trigger outside the enable window) the SBC-reset is

switched to active.

NormalRequest, Sleep And Emergency Mode

Watchdog is not active in this modes.

When SBC Is In The

Following Mode

CAN Transceiver

Can Be In

Reset condition

Bus Standby mode

NormalRequest

Bus Standby mode

Normal

RXTX or RXOnly or BusStandby

Standby

Bus Standby

Sleep

Bus Standby

Emergency

Bus Standby

Normal & V2 off (over load)

(note)

Bus standby

Note: In case V2 is turned off either by SPI command

(standby mode) or by the SBC itself due to V2 over load

condition (V2 short to gnd or V2 over temperature) the CAN is

automatically set into the Bus standby mode and does not

return to TXRX mode automatically when V2 is back to 5V.

The CAN must be re configured to TXRX or RXonly mode

after a V2 turn off.

Watchdog

General

The software window watchdog function is used to

monitors the microcontroller operation in Normal and in

Standby modes. The window watchdog timing is derived from

the SBC-clock. The desired watchdog timing must be first

transmitted during the SBC configuration, in NormalRequest

mode, via SPI to SWCR register. It can also be changed later

on. Selectable watchdog timings are 5ms, 10ms, 20ms,

33ms, 50ms, 75ms, 100ms and 200ms. These timings

correspond to the full disable window plus full enable window.

Figure 15. Window Watchdog Timing

earliest trigger time

watchdog trigger

50%

SBC watchdog window

disabled window

50%

enable window

latest

trigger

time

nom. trigger period

SBC-Reset OUT

Watchdog Timing

time out

latest

reset

time

As soon as the watchdog trigger is received in the enable

window, the internal counter is reset and start a new disable

window. The SBC triggers the watchdog word at CSB low to

high transition. Any watchdog trigger outside the enable

window leads to SBC reset.

In Normal and Standby Modes

For More Information On This Product,

MC33389

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