MC33910G5AC/MC3433910G5AC
FUNCTIONAL DEVICE OPERATIONS
OPERATIONAL MODES
In order to select and activate direct wake-up from L1
RESET
input, the Wake-up Control Register (WUCR) must be
configured with appropriate L1WE input enabled or disabled.
The wake-up input’s state is read through the Wake-up
Status Register (WUSR).
To reset a MCU the 33910 drives the RST pin low for the
time the reset condition lasts.
After the reset source is removed, the state machine will
drive the RST output low for at least 1.0 ms (typical value)
before driving it high.
L1 input is also used to perform cyclic-sense wake-up.
Note: Selecting an L1 input in the analog multiplexer
before entering low power mode will disable the wake-up
capability of the L1 input
In the 33910, four main reset sources exist:
5.0 V Regulator Low-voltage-Reset (VRSTTH
)
The 5.0 V regulator output VDD is continuously monitored
against brown outs. If the supply monitor detects that the
voltage at the VDD pin has dropped below the reset threshold
VRSTTH the 33910 will issue a reset. In case of over-
temperature, the voltage regulator will be disabled and the
voltage monitoring will issue a VDDOT Flag independently of
the VDD voltage.
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 line (L1) a state change occurs.
One or both HSx switch can be 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.
Window Watchdog Overflow
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:
If the watchdog counter is not properly serviced while its
window is open, the 33910 will detect an MCU software run-
away and will reset the microcontroller.
In WUCR: select the L1 input to WU-enable.
In HSCR: enable the desired HSx.
Wake-up From Sleep Mode
During Sleep mode, the 5.0 V regulator is not active,
hence all wake-up requests from Sleep mode require a
power-up/reset sequence.
• In TIMCR: select the CS/WD bit and determine the
cyclic sense period with CYSTx bits.
• Perform Goto Sleep/Stop command.
External Reset
Forced Wake-up
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.
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:
After the RST pin is released, there is no extra tRST to be
considered.
• In TIMCR: select the CS/WD bit and determine the low
power mode period with CYSTx bits.
WAKE-UP CAPABILITIES
• In HSCR: all HSx bits must be disabled.
Once entered into one of the low-power modes (Sleep or
Stop) only wake-up sources can bring the device into Normal
mode operation.
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.
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 5.0 V regulator and resetting the MCU. In both
cases the MCU can detect the wake-up source by accessing
the SPI registers and reading the Interrupt Source Register.
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.
LIN Wake-up
While in the low-power mode, the 33910 monitors the
activity on the LIN bus. A dominant pulse larger than tPROPWL
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. The bit RXONLY = 1 from LINCR
Register disables the LIN wake-up from Stop mode.
Wake-up from Wake-up input (L1) with cyclic sense
disabled
The wake-up line is dedicated to sense state changes of
external switch and wake-up the MCU (in Sleep or Stop
mode).
33910
Analog Integrated Circuit Device Data
Freescale Semiconductor
30
FREESCALE [ Freescale ]
