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Analog Integrated Circuit Device Data
22
Freescale Semiconductor
33389
FUNCTIONAL DEVICE OPERATION
OPERATIONAL MODES
OPERATIONAL MODES
CAN Transceiver Modes
The CAN transceiver has its own functioning modes:
RXTX mode, Term VBAT/Term VCC mode, and RX Only
mode. They are controlled by the Transceiver Control/Status
Register (TCR).
RXTX mode—Full transmitting and receiving capabilities
are enabled. Full failure detection is enabled.
Note: Standard/RXTX and Extended/RXTX are
equivalent.
RX Only mode—The transmitter is disabled but the
receive portion of the transceiver remains active. In this
mode, RX reports bus and TX activity (RX = TX or Bus
dominant).
Note: Standard/RX Only and Extended/RX Only are
equivalent.
Bus Stand-by mode—Is the Low Power mode for the CAN
transceiver. The driver and receivers are disabled. Wake-
up capability on both bus lines as well as Failure 3, 4, 7,
and 8 detection are enabled. RTL termination is set to
VBAT in the Bus Stand-by mode.
Low Power Modes
The transceiver provides a Low Power mode, entered and
exited by a SPI command. This is the Bus Stand-by mode
having the lowest power consumption for the transceiver.
CANL is biased to the battery voltage via the RTL output and
the pull-up current source on CANL and pull down current
source on CANH are disabled. Wake-up requests are
recognized by the transceiver when a dominant state is
detected on either bus wake-up lines. On a Bus wake-up
request, the SBC will activate the INT output or, if it is in the
Sleep mode, switch to the Normal Request mode. This event
is stored in the Wake-Up Input Status Register (WUISR).
To prevent a false wake-up resulting from transients or
(RF) fields, wake-up threshold levels have to be maintained
for a certain time. While in the Transceiver Low Power mode,
failure detection circuit remains partly active preventing
increased power consumption in cases of error 3, 4, 7, and 8.
Power-On
After the VBAT supply is switched ON, the SBC is in
Normal Request mode. Bus Stand-by is the corresponding
mode for the CAN transceiver.
The CAN transceiver is supplied by V2. As long as V2 is
below its under voltage threshold, the transceiver is forced to
Bus Stand-by mode (fail safe property).
SBC MODES
Global Power Save Concept
The SBC minimizes power consumption of the ECU.
Several operating modes are available to go to low power
consumption when the full activity is not required. Several
possibilities are provided to wake-up the ECU. This permits
peripherals or the microcontroller to be switched OFF when
no activity on the ECU is required.
Two switchable independent supply voltages (V1 and V2)
are provided for optimum ECU power management.
Generalities
The SBC can be operated in four modes:
1. Sleep
2. Stand-by
3. Normal
4. Emergency
After reset, the 33389 is automatically initialized to the
temporary mode, Normal Request, while waiting for
microcontroller configuration.
Reset Mode
This mode is entered after SBC power-up, or if an incorrect
software watchdog trigger occurs. The minimum duration for
reset mode is 1.0 ms typical, and unless there is a V1 failure
condition, the SBC enters the Normal Request mode after
reset.
In the case of a V1 failure condition leading to V1 low (ex:
short to ground), the SBC switches to the Reset mode. If V1
is still below the reset threshold after 100 ms, the behavior
depends upon the device version A or C:
C version: The 33389CDW and the 33389CDH will remain
in the reset mode.
D version: The 33389DDW and the 33389DEG will remain
in the reset mode. Note that the reset mode threshold for
the D version is slightly higher than the C version.
Normal Request Mode
The Normal Request mode is the Default mode after
33389 reset. V1 is active, while V2 and V3 are passive. The
SBC is not configured. The default values are set in the
registers. The SBC awaits data configuration via the SPI.
If no SPI data is received 75 ms after the Reset is
released, the SBC switches itself into the Sleep mode.
The software timing word (in SWCR) provides the data the
SBC must receive to consider when the microcontroller
begins the configuration sequence. Once received, this
software timing word, and the watchdog timer, become
active. Any other control data can then be sent from the
microcontroller to SBC.
The watchdog is not active in the Normal Request mode
before the software timing word is programmed into the SBC.
In this mode, neither V2 nor the CAN transmitter are active.