33910 Datasheet, PDF (26/44 Pages) Freescale Semiconductor, Inc – LIN System Basis Chip with 2x60mA High Side Drivers

FUNCTIONAL DEVICE OPERATIONS
OPERATIONAL MODES
temperature, the voltage regulator will be disabled and the
voltage monitoring will issue a VDDOT Flag independently of
the V_DD voltage.
Window Watchdog Overflow
If the watchdog counter is not properly serviced while its
window is open, the 33910 will detect a MCU software
runaway and will reset the microcontroller.
Wake-up From Sleep Mode
During Sleep Mode, the 5V regulator is not active, hence
all wake-up requests from Sleep Mode require a power-up/
reset sequence.
External Reset
The 33910 has a bidirectional reset pin which drives the
device to a safe state (same as Reset Mode) for as long as
this pin is held low. The RST pin must be held low long
enough to pass the internal glitch filter and get recognized by
the internal reset circuit. This functionality is also active in
Stop Mode.
After the RST pin is released, there is no extra t _RST to be
considered.
WAKE-UP CAPABILITIES
Once entered in to one of the low-power modes (Sleep or
Stop) only wake-up sources can bring the device into Normal
Mode operation.
In Stop Mode, a wake-up is signaled to the MCU as an
interrupt, while in Sleep Mode the wake-up is performed by
activating the 5V regulator and resetting the MCU. In both
cases the MCU can detect the wake-up source by accessing
the SPI registers. There is no specific SPI register bit to signal
a CS wake-up or external reset. If necessary this condition is
detected by excluding all other possible wake-up sources.
Wake-up From Wake-up Input (L1) With Cyclic Sense
Disabled
The wake-up line is dedicated to sense state changes of
external switches and wake-up the MCU (in Sleep or Stop
Mode).
In order to select and activate direct wake-up from the L1
input, the wake-up control register (WUCR) must be
configured with L1WE input enabled. The wake-up input
state is read through the wake-up status register (WUSR).
L1 input is also used to perform cyclic-sense wake-up.
Note: Selecting the L1 input in the analog multiplexer
before entering Low Power Mode will disable the wake-up
capability of the L1 input.
Wake-up From Wake-up Input (L1) With Cyclic Sense
Timer Enabled
The SBCLIN can wake-up at the end of a cyclic sense
period if on the wake-up input lines (L1) a state change
occurs. The HSx switch is activated in Sleep or Stop Modes
from an internal timer. Cyclic sense and force wake-up are
exclusive. If cyclic sense is enabled, the force wake-up can
not be enabled.
In order to select and activate the cyclic sense wake-up
from the L1 input, before entering in low power modes (Stop
or Sleep Modes), the following SPI set-up has to be
performed:
• In WUCR: select the L1 input to WU-enable.
• In HSCR: enable HSx.
• In TIMCR: select the CS/WD bit and determine the
cyclic sense period with CYSTx bits.
• Perform Goto Sleep/Stop command.
Forced Wake-up
The 33910 can wake-up automatically after a
predetermined time spent in Sleep or Stop Mode. Cyclic
sense and forced wake-up are exclusive. If forced wake-up is
enabled, the cyclic sense can not be enabled.
To determine the wake-up period, the following SPI set-up
has to be sent before entering in Low Power Modes:
• In TIMCR: select the CS/WD bit and determine the Low
Power Mode period with CYSTx bits.
• In HSCR: the HSx bit must be disabled.
CS Wake-up
While in Stop Mode, a rising edge on the CS will cause a
wake-up. The CS wake-up does not generate an interrupt
and is not reported on SPI.
LIN Wake-up
While in the low power modes the 33910 monitors the
activity on the LIN bus. A dominant pulse larger than t_PROPWL
followed by a dominant to recessive transition will cause a
LIN wake-up. This behavior protects the system from a short-
to-ground bus condition.
RST Wake-up
While in Stop Mode, the 33910 can wake-up when the
RST pin is held low long enough to pass the internal glitch
filter. Then, the 33910 will change to Normal Request or
Normal modes depending on the WDCONF pin
configuration. The RST wake-up does not generate an
interrupt and is not reported via SPI.
From Stop Mode, the following wake-up events can be
configured:
• Wake-up from L1 input without cyclic sense
• Cyclic sense wake-up inputs
• Force wake-up
• CS wake-up
• LIN wake-up
• RST wake-up
From Sleep Mode, the following wake-up events can be
configured:
• Wake-up from L1 input without cyclic sense
33910
26
Analog Integrated Circuit Device Data
Freescale Semiconductor