FUNCTIONAL DEVICE OPERATIONS
OPERATIONAL MODES
FUNCTIONAL DEVICE OPERATIONS
OPERATIONAL MODES
NORMAL MODE
Introduction
In Normal Mode, all 33912 functions are active and can be
controlled by the SPI interface and the PWMIN pin.
The 33912 offers three main operating modes: Normal
(Run), Stop, and Sleep (Low Power). In Normal Mode, the
device is active and is operating under normal application
conditions. The Stop and Sleep Modes are low-power modes
with wake-up capabilities.
The VDD regulator is ON and delivers its full current
capability.
If an external resistor is connected between the WDCONF
pin and the Ground, the window watchdog function will be
enabled.
In Stop Mode, the voltage regulator still supplies the MCU
with VDD (limited current capability), while in Sleep Mode the
voltage regulator is turned off (VDD = 0 V).
The wake-up inputs (L1-L4) can be read as digital inputs
or have its voltage routed through the analog-multiplexer.
Wake-up from Stop Mode is initiated by a wake-up
interrupt. Wake-up from Sleep Mode is done by a reset and
the voltage regulator is turned back on.
The LIN interface has slew rate and timing compatible with
the LIN protocol specification 2.0. The LIN bus can transmit
and receive information.
The selection of the different modes is controlled by the
MOD1:2 bits in the Mode Control Register (MCR).
The high side and low side switches are active and have
PWM capability according to the SPI configuration.
Figure 15 describes how transitions are done between the
different operating modes. Table 5, 27, gives an overview of
the operating modes.
The interrupts are generated to report failures for VSUP
over/under -voltage, thermal shutdown, or thermal shutdown
prewarning on the main regulator.
RESET MODE
The 33912 enters the Reset Mode after a power up. In this
mode, the RST pin is low for 1ms (typical value). After this
delay, it enters the Normal Request Mode and the RST pin is
driven high.
SLEEP MODE
The Sleep Mode is a low power mode. From Normal
Mode, the device enters into Sleep Mode by sending one SPI
command through the Mode Control Register (MCR). All
blocks are in their lowest power consumption condition. Only
some wake-up sources (wake-up inputs with or without cyclic
sense, forced wake-up and LIN receiver) are active. The 5V
regulator is OFF. The internal low-power oscillator may be
active if the IC is configured for cyclic-sense. In this condition,
one of the high side switches is turned on periodically and the
wake-up inputs are sampled.
The Reset Mode is entered if a reset condition occurs (VDD
low, watchdog trigger fail, after wake-up from Sleep Mode,
Normal Request Mode timeout occurs).
NORMAL REQUEST MODE
This is a temporary mode automatically accessed by the
device after the Reset Mode, or after a wake-up from Stop
Mode.
Wake-up from Sleep Mode is similar to a power-up. The
device goes in Reset Mode except that the SPI will report the
wake-up source and the BATFAIL flag is not set.
In Normal Request Mode, the VDD regulator is ON, the
RESET pin is High, and the LIN is operating in RX Only
Mode.
STOP MODE
As soon as the device enters in the Normal Request Mode
an internal timer is started for 150ms (typical value). During
these 150ms, the MCU must configure the Timing Control
Register (TIMCR) and the Mode Control Register (MCR) with
MOD2 and MOD1 bits set = 0, to enter the Normal Mode. If
within the 150ms timeout, the MCU does not command the
33912 to Normal Mode, it will enter in Reset Mode. If the
WDCONF pin is grounded in order to disable the watchdog
function, it goes directly in Normal Mode after the Reset
Mode. If the WDCONF pin is open, the 33912 stays typically
for 150ms in Normal Request before entering in Normal
Mode.
The Stop Mode is the second low power mode, but in this
case the 5V regulator is ON with limited current drive
capability. The application MCU is always supplied while the
33912 is operating in Stop Mode.
The device can enter into Stop Mode only by sending the
SPI command. When the application is in this mode, it can
wake-up from the 33912 side (for example: cyclic sense,
force wake-up, LIN bus, wake inputs) or the MCU side (CS,
RST pins). Wake-up from Stop Mode will transition the 33912
to Normal Request Mode and generates an interrupt except
if the wake-up event is a low to high transition on the CS pin
or comes from the RST pin.
33912
Analog Integrated Circuit Device Data
Freescale Semiconductor
25
FREESCALE [ Freescale ]
