33812 Datasheet, PDF (13/25 Pages) Freescale Semiconductor, Inc – SMALL ENGINE CONTROL IC

FUNCTIONAL DESCRIPTION
FUNCTIONAL PIN DESCRIPTION
are normally low and will go high when a fault is detected.
Toggling the respective input pin will clear the respective fault
pin if the fault has been cleared.
K-LINE COMMUNICATION (MTX, MRX, ISO9141)
These three pins are used to provide an ISO914, K-line
communication link for the MCU to provide diagnostic support
for the system. MRX is the +5.0 V logic level serial output line
to the MCU. MTX is the +5.0 V logic level serial input to the
IC from the MCU. The ISO9141 pin is a bidirectional line,
consistent with the ISO9141 specification for signalling to and
from the MCU.
RESET (RESET)
The RESET pin is an open drain output.Without power on
the circuit, RESET is held low by an internal pull-down
resistor. When power is applied to the circuit and the voltage
on the VCC_SENSE pin reaches the lower voltage threshold,
(5.0 volts - 2% = 4.9 V) the RESET pin will remain at a low
level (open drain FET turned on) for a period of time equal to
the value WD_RESET. After this time period, the RESET pin will
then go high and stay high until a watchdog RESET is
generated, or an under-voltage event on VCC occurs. The
watchdog time and refresh features are controlled via the
WDRFSH line.
RELOAD AND REFRESH TIME (WDRFSH)
The WDRFSH pin is an input that is supplied by an MCU
output to set up the initial reload time, WD_RELOAD, and to
refresh the watchdog timer. See the description of the
watchdog timer for information on how to use this pin.
WATCHDOG INHIBIT(WD_INH)
The WD_INH, watchdog inhibit pin, is normally tied to
ground. If desired, during software development, it can be
lifted from the ground pad and pulled high through an external
pull-up resistor. When high, WD_INH will prevent the
watchdog timer from causing a RESET because of a
watchdog timeout. The WD_INH should not be connected to
an MCU I/O pin or left floating in normal operation.
TEST PINS (TEST1, TEST2, AND TEST3)
These three pins are used only by Freescale test
engineering during the production testing of the 33812. They
are not to be used for any application purpose and must be
handled as specified in the pinout section of this document.
Analog Integrated Circuit Device Data
Freescale Semiconductor
33812
13