33389 datasheet(24/49 Pages) FREESCALE

24 / 49 page

Analog Integrated Circuit Device Data

Freescale Semiconductor

33389

FUNCTIONAL DEVICE OPERATION

OPERATIONAL MODES

Figure 8. Typical Behavior at Power-On

Note: In the Normal Request mode, if a SPI command is

received before the software timing configuration (SWCR

for the go-to Emergency mode).

Correspondence Between SBC and CAN Transceiver

Modes

Table 14 provides different possible CAN transceiver

modes versus SBC modes.

Watchdog

The software window watchdog function monitors the

microcontroller operation in the Normal and Stand-by modes.

The window watchdog timing is derived from the SBC clock.

The desired watchdog timing must be first transmitted during

the SBC configuration, in the Normal Request mode, via SPI

to SWCR. It can also be changed later on. Selectable

watchdog timings are 5.0 ms, 10 ms, 20 ms, 33 ms, 50 ms,

75 ms, 100 ms and 200 ms. These timings correspond to the

full disable window plus full enable window.

Figure 9. Window Watchdog Timing

As soon as the watchdog trigger is received in the Enable

Window, the internal counter is reset and begins a new

disable window. The SBC triggers the watchdog word at CS

low-to-high transition. Any watchdog trigger outside the

Enable Window leads to an SBC reset.

• Normal and Stand-by Modes— The SBC get the watchdog

word from the microcontroller via SPI in the Normal mode.

In case of a trigger time failure (no trigger or trigger outside

the Enable Window) the SBC reset is switched to active.

• Normal Request, Sleep, and Emergency Mode—

Watchdog is not active in these modes.

WAKE-UP CAPABILITIES

Several wake-up capabilities are available.

Forced Wake-Up

The forced wake-up is enabled and disabled by SPI in the

V3 register. It is used to automatically wake-up the system by

supplying V1 with proper reset in the Sleep mode. This

corresponds to jump into the Normal Request mode. If the

SBC is not properly configured within 75 ms, it switches back

to the Sleep mode until the next wake-up. If both Cyclic

Sense and Forced Wake-Up are enabled by the SPI while in

the Sleep mode, only Cyclic Sense is active.

The period of Forced Wake-Up are 32 ms, 64 ms, 128 ms,

256 ms, 512 ms, 1024 ms, 2048 ms, and 8192 ms chosen by

SPI in the Cyclic Timing Control Register (CYTCR).

Wake-Up Inputs (Local Wake-Up)/Cyclic Sense

SBC provides three wake-up inputs to monitor external

events such as closing/opening of switches. The wake-up

feature is available in Normal, Stand-by, and Sleep modes.

Table 14. CAN Modes vs. SBC Modes

When SBC Is In The Following

Mode

CAN Transceiver

Can Be In

Reset Condition

Bus Stand-by Mode

Normal Request

Bus Stand-by Mode

Normal

RXTX or RXOnly or BusStand-by

Stand-by

Bus Stand-by

Sleep

Bus Stand-by

Emergency

Bus Stand-by

Normal and V2 OFF (over load)

In case V2 is turned OFF either

by SPI command (Stand-by

mode) or by the SBC itself due

to V2 over load condition (V2

short to ground or V2 over tem-

perature) the CAN is automati-

cally set into the Bus Stand-by

mode and does not return to

TXRX mode automatically

when V2 is back to 5.0 V. The

CAN must be re configured to

TXRX or RX Only mode after a

V2 turn OFF

Bus Stand-by

ECU

connected

to battery

Reset

V1 low

Normal

Sleep

Normal

V1 on

SPI SW

timing configuration

at t<75ms

No SPI SW

timing configuration

at t=75ms

(reset

released

)

Emergency

SPI go to Emergency

at t<75ms

Request

Watchdog Trigger

SBC Watchdog Window

Earliest Trigger Time

Latest

Disabled Window

Nom. Trigger Period

Time Out

Latest

SBC-Reset OUT

50%

Watchdog Timing

Enable Window

Reset

Trigger

Time

33389 Datasheet(PDF) 24 Page - Freescale Semiconductor, Inc

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