33812 datasheet(13/25 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

33812

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 VCCSENSE 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 WDRESET. 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, WDRELOAD, 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.

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