TJA1082 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2012. All rights reserved.
Product data sheet Rev. 6 — 28 November 2012 7 of 38
NXP Semiconductors
TJA1082
FlexRay node transceiver
6.1.1.1 Bus activity and idle detection
In Normal mode, bus activity and bus idle are detected as follows:
• Bus activity is detected when the absolute differential voltage on the bus lines is
higher than V
i(dif)det(act)
for t
det(act)(bus)
:
– If the differential voltage on the bus lines is lower than V
IL(dif)
after bus activity has
been detected, pin RXD switches LOW.
– If the differential voltage on the bus lines is higher than V
IH(dif)
after bus activity has
been detected, pin RXD remains HIGH.
• Bus idle is detected when the absolute differential voltage on the bus lines is lower
than V
i(dif)det(act)
for t
det(idle)(bus)
. This results in pin RXD being switched HIGH or
staying HIGH.
6.1.2 Standby mode
Standby mode is a low-power mode featuring very low current consumption. In Standby
mode, the transceiver is unable to transmit or receive data since both the transmitter and
the normal receiver are switched off. The low-power receiver is activated to monitor the
bus for wake-up activity, provided an undervoltage has not been detected on pin V
CC
.
The low-power receiver is deactivated if an undervoltage is detected on pin V
CC
- with the
result that the wake flag is not set if a wake-up pattern or dedicated data frame is
received.
Pins ERRN and RXD indicate the status of the wake flag when V
IO
and V
CC
are within
their operating ranges. See Table 3
for a description of pins ERRN and RXD when an
undervoltage is detected on pin V
IO
or pin V
CC
.
The status register cannot be read via the SPI interface if an undervoltage is detected on
pin V
IO
.
The BGE input has no effect in Standby mode.
6.1.3 Power-off mode
The transmitter and the two receivers (normal and low-power) are deactivated in
Power-off mode. As a result, the wake flag is not set if a wake-up pattern or dedicated
data frame is received. If the voltage at V
CC
rises above V
th(rec)POR
, the transceiver
switches to Standby mode and the digital section is reset. If V
CC
subsequently drops
below V
th(det)POR
, the transceiver reverts to Power-off mode (see Section 6.2).
The status register cannot be read via the SPI interface in Power-off mode.
6.1.4 State transitions
Figure 4 shows the TJA1082 state transition diagram. The timing diagram for the ERRN
indication signal during transitions between Normal and Standby modes, when the error
flag is set and the wake flag is not set, is illustrated in Figure 5
and described in Table 6.
