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UJA1069TW/5V0/C/T,

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P27P28-P30P31-P33P34-P36P37-P39P40-P42P43-P45P46-P48P49-P51P52-P54P55-P57P58-P60P61-P63P64-P64
UJA1069_4 © NXP B.V. 2009. All rights reserved.
Product data sheet Rev. 04 — 28 October 2009 10 of 64
NXP Semiconductors
UJA1069
LIN fail-safe system basis chip
Interrupts from SBC to the host microcontroller are also monitored. A system reset is
performed if the host microcontroller does not respond within t
RSTN(INT)
. Entering Normal
mode does not activate the LIN transceiver automatically. The LIN Mode Control (LMC) bit
must be used to activate the LIN medium if required, allowing local cyclic wake-up
scenarios to be implemented without affecting the LIN-bus.
6.2.5 Standby mode
In Standby mode the system is set into a state with reduced current consumption. The
watchdog will, however, continue to monitor the microcontroller (Time-out mode) since it is
powered via pin V1.
In the event that the host microcontroller can provide a low-power mode with reduced
current consumption in its Standby mode or Stop mode, the watchdog can be switched off
entirely in Standby mode of the SBC. The SBC monitors the microcontroller supply current
to ensure that there is no unobserved phase with disabled watchdog and running
microcontroller. The watchdog will remain active until the supply current drops below
I
thL(V1)
. Below this current limit the watchdog is disabled.
Should the current increase to I
thH(V1)
, e.g. as result of a microcontroller wake-up from
application specific hardware, the watchdog will start operating again with the previously
used time-out period. If the watchdog is not triggered correctly, a system reset will occur
and the SBC will enter Start-up mode.
If Standby mode is entered from Normal mode with the selected watchdog OFF option,
the watchdog will use the maximum time-out as defined for Standby mode until the supply
current drops below the current detection threshold; the watchdog is now OFF. If the
current increases again, the watchdog is immediately activated, again using the maximum
watchdog time-out period. If the watchdog OFF option is selected during Standby mode,
the last used watchdog period will define the time for the supply current to fall below the
current detection threshold. This allows the user to align the current supervisor function to
the application needs.
Generally, the microcontroller can be activated from Standby mode via a system reset or
via an interrupt without reset. This allows implementation of differentiated start-up
behavior from Standby mode, depending on the application needs:
• If the watchdog is still running during Standby mode, the watchdog can be used for
cyclic wake-up behavior of the system. A dedicated Watchdog Time-out Interrupt
Enable (WTIE) bit enables the microcontroller to decide whether to receive an
interrupt or a hardware reset upon overflow. The interrupt option will be cleared in
hardware automatically with each watchdog overflow to ensure that a failing main
routine is detected while the interrupt service still operates. So the application
software must set the interrupt behavior each time before a standby cycle is entered.
• Any wake-up via the LIN-bus together with a local wake-up event will force a system
reset event or an interrupt to the microcontroller. So it is possible to exit Standby mode
without any system reset if required.
When an interrupt event occurs the application software has to read the Interrupt register
within t
RSTN(INT)
. Otherwise a fail-safe system reset is forced and Start-up mode will be
entered. If the application has read out the Interrupt register within the specified time, it
can decide whether to switch into Normal mode via an SPI access or to stay in Standby
mode.
UJA1069_4 © NXP B.V. 2009. All rights reserved.
Product data sheet Rev. 04 — 28 October 2009 11 of 64
NXP Semiconductors
UJA1069
LIN fail-safe system basis chip
The following operations are possible from Standby mode:
• Cyclic wake-up by the watchdog via an interrupt signal to the microcontroller (the
microcontroller is triggered periodically and checked for the correct response)
• Cyclic wake-up by the watchdog via a reset signal (a reset is performed periodically;
the SBC provides information about the reset source to allow different start
sequences after reset)
• Wake-up by activity on the LIN-bus via an interrupt signal to the microcontroller
• Wake-up by bus activity on the LIN-bus via a reset signal
• Wake-up by increasing the microcontroller supply current without a reset signal
(where a stable supply is needed for the microcontroller RAM contents to remain valid
and wake-up from an external application not connected to the SBC)
• Wake-up by increasing the microcontroller supply current with a reset signal
• Wake-up due to a falling edge at pin WAKE forcing an interrupt to the microcontroller
• Wake-up due to a falling edge at pin WAKE forcing a reset signal
6.2.6 Sleep mode
In Sleep mode the microcontroller power supply (V1) and the INH/LIMP controlled
external supplies are switched off entirely, resulting in minimum system power
consumption. In this mode, the watchdog runs in Time-out mode or is completely off.
Entering Sleep mode results in an immediate LOW level on pin RSTN, thus stopping any
operation of the microcontroller. The INH/LIMP output is floating in parallel and pin V1 is
disabled. It is also possible for V3 to be ON, OFF or in Cyclic mode to supply external
wake-up switches.
If the watchdog is not disabled in software, it will continue to run and force a system reset
upon overflow of the programmed period time. The SBC enters Start-up mode and pin V1
becomes active again. This behavior can be used for a cyclic wake-up from Sleep mode.
Depending on the application, the following operations can be selected from Sleep mode:
• Cyclic wake-up by the watchdog (only in Time-out mode); a reset is performed
periodically, the SBC provides information about the reset source to allow different
start sequences after reset
• Wake-up by activity on the LIN-bus or falling edge at pin WAKE
• An overload on V3, only if V3 is in a cyclic or in continuously ON mode
6.2.7 Flash mode
Flash mode can only be entered from Normal mode by entering a specific Flash mode
entry sequence. This fail-safe control sequence comprises three consecutive write
accesses to the Mode register, within the legal windows of the watchdog, using the
operating mode codes 111, 001 and 111 respectively. As a result of this sequence, the
SBC will enter Start-up mode and perform a system reset with the related reset source
information (bits RSS[3:0] = 0110).
UJA1069_4 © NXP B.V. 2009. All rights reserved.
Product data sheet Rev. 04 — 28 October 2009 12 of 64
NXP Semiconductors
UJA1069
LIN fail-safe system basis chip
From Start-up mode the application software now has to enter Flash mode within t
WD(init)
by writing Operating Mode code 011 to the Mode register. This feeds back a successfully
received hardware reset (handshake between the SBC and the microcontroller). The
transition from Start-up mode to Flash mode is possible only once after completing the
Flash entry sequence.
The application can also decide not to enter Flash mode but to return to Normal mode by
using the Operating Mode code 101 for handshaking. This erases the Flash mode entry
sequence.
The watchdog behavior in Flash mode is similar to its time-out behavior in Standby mode,
but Operating mode code 111 must be used for serving the watchdog. If this code is not
used or if the watchdog overflows, the SBC immediately forces a reset and enters Start-up
mode. Flash mode is properly exited using the Operating Mode code 110 (leave Flash
mode), which results in a system reset with the corresponding reset source information.
Other Mode register codes will cause a forced reset with reset source code ‘illegal Mode
register code’.
6.3 On-chip oscillator
The on-chip oscillator provides the clock signal for all digital functions and is the timing
reference for the on-chip watchdog and the internal timers.
If the on-chip oscillator frequency is too low or the oscillator is not running at all, there is
an immediate transition to Fail-safe mode. The SBC will stay in Fail-safe mode until the
oscillator has recovered to its normal frequency and the system receives a wake-up event.
6.4 Watchdog
The watchdog provides the following timing functions:
• Start-up mode; needed to give the software the opportunity to initialize the system
• Window mode; detects too early and too late accesses in Normal mode
• Time-out mode; detects a too late access, can also be used to restart or interrupt the
microcontroller from time to time (cyclic wake-up function)
• OFF mode; fail-safe shut-down during operation thus preventing any blind spots in the
system supervision
The watchdog is clocked directly by the on-chip oscillator.
To guarantee fail-safe control of the watchdog via the SPI, all watchdog accesses are
coded with redundant bits. Therefore, only certain codes are allowed for a proper
watchdog service.
The following corrupted watchdog accesses result in an immediate system reset:
• Illegal watchdog period coding; only ten different codes are valid
• Illegal operating mode coding; only six different codes are valid
Any microcontroller driven mode change is synchronized with a watchdog access by
reading the mode information and the watchdog period information from the same
register. This enables an easy software flow control with defined watchdog behavior when
switching between different software modules.
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UJA1069TW/5V0/C/T,

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Buy UJA1069TW/5V0/C/T,
Manufacturer:
NXP Semiconductors
Description:
LIN Transceivers IC LIN FAIL-SAFE
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