33902 datasheet(16/31 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

33902

FUNCTIONAL DEVICE OPERATION

OPERATIONAL MODES

The flag is cleared by leaving the Normal mode or by a

P_SPI reading.

WAKE Pin - Local Wake-up (WU)

From the Standby, Go To Sleep or Sleep mode, this flag is

set if a transition on the WAKE pin is detected. This wake-up

is reported on the ERR pin by a low level in Standby mode,

as well as in Sleep mode if VIO is present.

The wake-up flag is cleared by leaving the Normal mode

or by P_SPI reading.

Wake-up Source

Wake-up source is reported on the ERR pin by entering

Normal mode, before 4 TX pulses. The ERR pin is low to

indicate a local wake-up, and high to indicate CAN wake-up.

Local Failure

This flag is a logic «OR» of the following failures: TXD

dominant clamping, RXD recessive clamping, TXD-to-RXD

short-circuit and VDD low condition. This flag is reported in

Listen Only on the ERR pin coming from Normal mode.

Using the P_SPI, it is possible to get detailed failure

information.

BUS Failure

The BUS failure flag is set if the CAN transceiver detects

a bus line short-circuit condition to VSUP, VDD, or GND,

during five consecutive dominant-recessive cycles on the

TXD pin. In addition, this flag reports a bus dominant

clamping condition. In Normal mode, the bus failure flag is

available on the ERR pin.

Using the P_SPI, it is possible to get detailed failure

information.

VDD low

VDD low flag is set in Normal and Listen Only mode when

VDD is below the VDD low threshold. After a time longer than

tVDD-CANOFF, the CAN is disabled and after a time longer than

tVDDOFF, the VDD regulator is disabled to avoid a battery

discharge.

If the CRANK bit is set high, the VDD regulator and CAN

will not be disabled if VSUP is below VSUV. When VSUP is

above VSUV, the CRANK bit has no effect.

VDD low flag is reported in Normal and Listen Only mode,

so the user can differentiate between local and bus failures

by changing modes and observing ERR staying low.

In case of a double failure (local and bus failure) at the

same time, the results will be the same: ERR low in Normal

and in Listen Only mode. However, this is unlikely to occur.

This flag is cleared when entering low power, or when VDD

is above VDD low threshold, plus the P_SPI reading.

The VDD regulator is re enabled as soon as VSUP rises

above VSUP low, or by a mode change (refer to the crank

pulse illustration).

The CAN is re-enabled as soon as VDD is above VDD low

threshold. (refer to crank pulse illustration).

ERR Pin

The ERR pin reports various information depending upon

the device state, the device state transition, and event on the

TXD pin.

Table 6 shows the diagnostic flag availability when the

device is controlled in a static manner.

Table 6. “Static” Diagnostic Flags

Flag

Accessibility

Clearing Diagnostic

BATFAIL

Listen-Only mode (coming from Standby, Go-to-Sleep, Sleep)

Leaving Normal mode

CANWU or Local WU

Standby, Go-to-Sleep, Sleep (provided VIO is present)

Leaving Normal mode or by setting the BATFAIL

Wake-up source

Normal mode (Before the fourth dominant to recessive edge on the

TXD pin)

Leaving Normal mode, or by setting BATFAIL flag.

BUS Failure

Normal mode (After the fourth dominant to recessive edge on the

TXD pin)

Re-entering Normal mode

Local Failure

Listen Only mode (coming from Normal mode)

Entering Normal mode or TXD high while RXD low.

VDD low

Normal mode (After the fourth dominant to recessive edge on the

TXD pin) and Listen Only mode (coming from Normal mode)

VDD > VDD low threshold

Evaluation mode

By RXD low, when coming from Sleep or Standby into Normal or

Listen Only modes.

RXD goes from low to high, to signal the device is ready

and has exited low power modes (TLP-NP parameter).

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