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 10 of 61
NXP Semiconductors
TJA1085
FlexRay active star coupler
6.5 Communication controller interface
6.5.1 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 V
i(dif)det(act)
 for
t
det(act)(bus)
, activity is detected on the bus lines
• If, after bus activity detection, the differential voltage on the bus lines is higher than
V
IH(dif)
, pin RXD will go HIGH
• If, after bus activity detection, the differential voltage on the bus lines is lower than
V
IL(dif)
, pin RXD will go LOW
• If the absolute differential voltage on the bus lines is lower than V
i(dif)det(act)
 for
t
det(idle)(bus)
, then idle is detected on the bus lines (pin RXD is switched HIGH or
remains HIGH)
Additionally, activity and idle can be detected:
• if pin TXEN is LOW for longer than t
det(act)(TXEN)
, activity is detected on pin TXEN
• if pin TXEN is HIGH for longer than t
det(idle)(TXEN)
, idle is detected on pin TXEN
• if pin TRXD0 or TRXD1 is LOW for longer than t
det(act)(TRXD)
, activity is detected on the
TRXD0/1 interface
• if pins TRXD0 and TRXD1 are both HIGH for longer than t
det(idle)(TRXD)
, idle is
detected on the TRXD0/1 interface
[1] The transmitter is activated by a falling edge on pin TXD while TXEN is LOW and BGE is HIGH.
[2] Internal pull-up resistor (R
pu
) to V
BUF
.
[3] BP and BM biased to GND.
Table 3. Transmitter input signals: TXD, TXEN and BGE
[1]
TXD TXEN BGE V
IO
UV
detected
RXD Bus TRXD0 TRXD1 Operating mode
X H X no HIGH idle high ohmic
[2]
high ohmic
[2]
AS_Normal
X X L no HIGH idle high ohmic
[2]
high ohmic
[2]
AS_Normal
L L H no LOW DATA_0 LOW high ohmic
[2]
AS_Normal
H L H no HIGH DATA_1 high ohmic
[2]
LOW AS_Normal
X X X no HIGH idle high ohmic
[2]
high ohmic
[2]
AS_Standby,
[3]
AS_Sleep
[3]
X X X yes LOW idle high ohmic
[2]
high ohmic
[2]
AS_Normal,
AS_Standby,
[3]
AS_Sleep
[3]
X X X X HIGH float high ohmic
[2]
high ohmic
[2]
AS_PowerOff, AS_Reset
Table 4. Bus as input
Bus V
IO
UV
detected
RXD TRXD0 TRXD1 Operating mode
DATA_0 no LOW LOW high ohmic
[1]
AS_Normal
DATA_1 no HIGH high ohmic
[1]
LOW AS_Normal
idle no HIGH high ohmic
[1]
high ohmic
[1]
AS_Normal
X no HIGH high ohmic
[1]
high ohmic
[1]
AS_Standby, AS_Sleep