Datasheet

TJA1085 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2012. All rights reserved.
Product data sheet Rev. 1 — 23 October 2012 12 of 61
NXP Semiconductors
TJA1085
FlexRay active star coupler
The UV_ERROR, CLAMP_ERROR, TEMP_ERROR and EVENT_BRx status bits are
reset after the flag (or flags) that triggered the interrupt has been reset and a successful
read operation had been performed (these two events can occur in any order). Resetting
these bits triggers a further falling edge on INTN to indicate to the host that the issue that
triggered the interrupt has been resolved (except in the case of EVENT_BRx if a branch
wake-up event triggered the interrupt). See Section 6.10.2.3
for further details.
INTN signaling conforms to the FlexRay Electrical Physical Layer specification V3.0.1
(see Ref. 1
).
6.8 Operating modes
The TJA1085 features five operating modes.
AS_PowerOff, AS_Sleep and AS_Standby are low-power modes in which the transceiver
is unable to transmit or receive data streams on the bus. In AS_PowerOff mode, only
power-on reset detection is active. The SPI, the low-power receiver and wake-up
detection are active in AS_Sleep mode. Undervoltage detection is enabled on V
CC
, V
BAT
and V
BUF
in AS_Standby and AS_Normal modes. V
IO
undervoltage detection is always
enabled, except when the TJA1085 is in AS_PowerOff mode.
In AS_Normal mode, the TJA1085 can transmit and receive data streams on the bus.
Pin INH is HIGH in AS_Normal, AS_Standby and AS_Reset, and floating in AS_PowerOff
and AS_Sleep.
The dStarGoToSleep timer is started when the TJA1085 switches to AS_Standby or
AS_Normal, or when idle is detected on the bus. The timer is halted and reset when
activity is detected on the bus.
6.8.1 Operating mode transitions
6.8.1.1 AS_PowerOff
The TJA1085 switches to AS_PowerOff from any mode if the internal supply to the state
machine, V
DIG
, falls below the power-on detection threshold voltage (V
th(det)POR
). It
remains in AS_PowerOff until V
DIG
rises above the power-on recovery threshold voltage
(V
th(rec)POR
), when it switches to AS_Standby. Pins INTN and SDO are switched to a
high-impedance state in AS_PowerOff mode.
6.8.1.2 AS_Reset
The TJA1085 switches to AS_Reset from any mode if pin RSTN goes LOW with no
undervoltage detected on V
IO
. It remains in AS_Reset until pin RSTN goes HIGH, when it
switches to AS_Standby.
6.8.1.3 AS_Standby
The TJA1085 switches to AS_Standby:
- from AS_PowerOff when V
DIG
rises above the power-on recovery threshold voltage
(V
th(rec)POR
)
- from AS_Reset when pin RSTN goes HIGH
- from AS_Normal when a V
CC
undervoltage event is detected (V
CC
<V
uvd(VCC)
for
longer than t
det(uv)(VCC)
)