TLE9221SX Datasheet, PDF (52/91 Pages) Infineon Technologies AG – FlexRay Transceiver

TLE9221SX
Operating Mode Description
9.3.1 Priorities of Undervoltage Events
Even if there are undervoltage events on both power supplies uV_BAT and uV_CC, together with an undervoltage
event on the reference supply uV_IO, the Central State Machine is operating and handles the undervoltage events.
An undervoltage event on uV_IO blocks the Host Interface at once and interrupts the communication before the uV_IO
undervoltage timer expires. When the uV_IO undervoltage timer expires, the TLE9221SX changes the mode of
operation to BD_Sleep. In case the uV_CC undervoltage flag is set, the uV_IO undervoltage flag overrules the uV_CC
undervoltage flag.
If the uV_CC undervoltage flag was set before the uV_IO undervoltage flag, the mode of operation changes from
BD_Standby to BD_Sleep mode.
If the uV_IO undervoltage flag was set before the uV_CC undervoltage flag, the mode of operation remains in
BD_Sleep mode.
During an uV_BAT undervoltage event, the Host Interface and also the Communication Controller Interface
continues to work until the undervoltage detection timer expires. The uV_BAT undervoltage flag also overrules a
uV_CC undervoltage flag and the transceiver TLE9221SX ends up in BD_Sleep mode. Simultaneous undervoltage
events at uV_BAT and uV_IO, additionally disable the Host Interface and the Communication Controller Interface in
comparison to a single uV_BAT undervoltage event. After the undervoltage detection timer expires, the TLE9221SX
changes over to BD_Sleep mode.
The least significant undervoltage flag is the uV_CC undervoltage flag. An active uV_CC undervoltage flag changes
the mode of operation from non-low power mode to BD_Standby mode, when no other undervoltage flag is set.
During an uV_CC undervoltage event the Transmitter is disabled.
9.4
Operating Mode Changes by Undervoltage Recovery
As stated in Chapter 8.3, any undervoltage flag causes a change in the operating mode and blocks the Host
Interface and the Communication Controller Interface.
After recovering from the undervoltage condition, and after the undervoltage flags are cleared, the FlexRay
transceiver TLE9221SX enables the Host Interface and also the Communication Controller Interface and the host
command applied at the inputs STBN and EN changes the mode of operation accordingly (see Figure 36 and
Table 15).
9.4.1 BD_Sleep Mode Entry Flag
A special case is the undervoltage recovery from BD_Sleep mode while the host command BD_Standby is applied
to the Host Interface.
According to the FlexRay EPL Specification, version 3.0.1, the EN input pin shall be disabled while the device is
in BD_Sleep mode. A mode changeover via host command from BD_Sleep mode to BD_Standby mode is not
permitted (compare with Table 13). In order to be compliant with the FlexRay Conformance Test version 3.0.1 it
is mandatory to distinguish the host command BD_Sleep from BD_Standby, after the transceiver recovers from
an undervoltage event.
The BD_Sleep mode entry flag indicates, how the changeover to BD_Sleep mode occurred. If changeover to
BD_Sleep mode took place by setting an undervoltage flag, the BDSME flag (BD_Sleep Mode Entry) is set to “low”
and the EN input pin remains active. If changeover to BD_Sleep mode took place by a host command, the BDSME
flag is set to logical “high” and the EN input pin gets disabled (see Table 15).
The BDSME is an internal flag and it is neither indicated at the ERRN output nor latched in the SIR.
Data Sheet
52
Rev. 1.10, 2013-07-15