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TJA1081

FlexRay node transceiver

NXP Semiconductors. 

NXP Semiconductors

TJA1081

FlexRay node transceiver

6. Functional description

The block diagram of the transceiver is shown in Figure 1.

6.1 Operating modes

The TJA1081 supports the following operating modes:

• Normal (normal-power mode)

• Receive-only (normal-power mode)

• Standby (low-power mode)

• Go-to-sleep (low-power mode)

• Sleep (low-power mode)

6.1.1 Bus activity and idle detection

The following mechanisms for activity and idle detection are valid in normal-power modes:

• If the absolute differential voltage on the bus lines is higher than |Vi(dif)det(act)| for

tdet(act)(bus), activity is detected on the bus lines and pin RXEN is switched LOW which

results in pin RXD being released:

– If, after bus activity detection, the differential voltage on the bus lines is higher than

VIH(dif), pin RXD will go HIGH

– If, after bus activity detection, the differential voltage on the bus lines is lower than

VIL(dif), pin RXD will go LOW

• If the absolute differential voltage on the bus lines is lower than |Vi(dif)det(act)| for

tdet(idle)(bus), then idle is detected on the bus lines and pin RXEN is switched to HIGH.

This results in pin RXD being blocked (pin RXD is switched to HIGH or stays HIGH)

6.2 Mode control pins: STBN and EN

Control inputs STBN and EN are used to select the operating mode. See Table 3 for a

detailed description of pin signalling and Figure 3 for the timing diagram.

All mode transitions are controlled via the STBN and EN pins, unless an undervoltage

condition is detected. If VIO and (VCC or VBAT) are within their specified operating ranges,

pin ERRN will indicate the status of the error flag.

Table 3. Pin signalling

Mode

STBN EN ERRN[1]

RXEN

RXD

Transmitter INH

LOW

HIGH LOW

HIGH LOW

HIGH

Normal

HIGH HIGH error flag error flag bus

Receive-only HIGH LOW set

reset

activity

bus bus DATA_0 bus DATA_1 enabled

idle

or idle

disabled

HIGH

Go-to-sleep LOW HIGH error flag error flag wake flag wake wake flag wake flag

Standby

LOW LOW set[2]

reset

set[2]

flag set[2]

reset

reset

Sleep

LOW X

float

[1] Pin ERRN provides a serial interface for retrieving diagnostic information.

[2] Valid if VIO and (VCC or VBAT) are present.

TJA1081_2

Product data sheet

Rev. 02 — 28 July 2009

© NXP B.V. 2009. All rights reserved.

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