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 16 of 61
NXP Semiconductors
TJA1085
FlexRay active star coupler
6.9 Branch operating modes
Each of the four branches in the TJA1085 features six branch operating modes:
• Branch_Off
All branches are in Branch_Off mode when the TJA1085 is in AS_PowerOff or
AS_Reset mode. The transmitter, normal receiver, low-power receiver and bus error
detection are disabled. The bus pins are floating.
• Branch_LowPower
All branches are in Branch_LowPower mode when the TJA1085 is in AS_Standby or
AS_Sleep mode. The transmitter, the normal receiver and bus error detection are
disabled. The low-power receiver is active (i.e. remote wake-up is possible). The bus
pins are biased to ground.
• Branch_Disabled
The TJA1085 switches to Branch_Disabled if an overtemperature is detected. The
‘Branch_Disabled’ and ‘Branch_Normal’ commands allow the host to enable/disable a
branch without affecting the remaining branches. The transmitter, normal receiver and
bus error detection are disabled. Only the low-power receiver is active (remote
wake-up is possible). The bus pins are biased to V
o(idle)(BP)
and V
o(idle)(BM)
.
• Branch_Normal
When a branch is in Branch_Normal, the TJA1085 will be in AS_Normal. The
transmitter, normal receiver and bus error detection are active. The bus pins are
biased to V
o(idle)(BP)
and V
o(idle)(BM)
.
• Branch_TxOnly1
In Branch_TxOnly1 mode, the receiver is disabled, i.e. the received data is not
forwarded to the signal router. The transmitter is active and bus error detection is
active. The bus pins are biased to V
o(idle)(BP)
and V
o(idle)(BM)
.
• Branch_TxOnly2
This mode is host-controlled only and is operationally identical to Branch_TxOnly1. It
allows the host to switch off the receiver in response to error conditions.
• Branch_FailSilent
The transmitter, the low-power receiver and bus error detection are disabled. Only the
receiver remains active to monitor the branch for idle or activity. Received data is not
forwarded to the signal router. The bus pins are biased to V
o(idle)(BP)
and V
o(idle)(BM)
.
6.9.1 Branch operating mode transitions
Branch-related host commands can only be issued when the TJA1085 is in AS_Normal
mode.
6.9.1.1 Branch_Off
When the TJA1085 enters AS_PowerOff or AS_Reset, all four branches switch to
Branch-Off. When the TJA1085 subsequently switches to AS_Standby, all four branches
switch to Branch_LowPower.
6.9.1.2 Branch_LowPower
All four branches switch to Branch_LowPower when the TJA1085 enters AS_Standby or
AS_Sleep. All branches remain in this mode until the TJA1085 enters AS_Normal. When
this transition happens, branches that were in Branch_Disabled before switching to
Branch_LowPower return to Branch_Disabled. The remaining branches switch to
Branch_Normal.