X40430/X40431 – Preliminary Information

Characteristics subject to change without notice.

3 of 24

REV 1.2.3 11/28/00

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8

SDA

Serial Data. SDA is a bidirectional pin used to transfer data into and out of the device. It has an

open drain output and may be wire ORed with other open drain or open collector outputs. This pin

requires a pull up resistor and the input buffer is always active (not gated).

Watchdog Input. A HIGH to LOW transition on the SDA (while SCL is toggled from HIGH to LOW

and followed by a stop condition) restarts the Watchdog timer. The absence of this transition within

the watchdog time out period results in WDO going active.

9

SCL

Serial Clock. The Serial Clock controls the serial bus timing for data input and output.

10

WP

Write Protect. WP HIGH prevents writes to any location in the device (including all the registers).

It has an internal pull down resistor.

11

V3MON

LOW. This input can monitor an unregulated power supply with an external resistor divider or can

not used.

12

V3FAIL

13

WDO

WDO Output. WDO is an active LOW, open drain output which goes active whenever the watch-

dog timer goes active.

14

Supply Voltage

PIN DESCRIPTION (Continued)

Pin

Name

Function

PRINCIPLES OF OPERATION

Power On Reset

Applying power to the X40430/31 activates a Power

On Reset Circuit that pulls the RESET/RESET pins

active. This signal provides several benefits.

– It prevents the system microprocessor from starting

to operate with insufficient voltage.

– It prevents the processor from operating prior to sta-

bilization of the oscillator.

– It allows time for an FPGA to download its configura-

tion prior to initialization of the circuit.

– It prevents communication to the EEPROM, greatly

reducing the likelihood of data corruption on power up.

(X40431) and RESET (X40430) pin allowing the system

to begin operation.

Figure 1. Connecting a Manual Reset Push-Button

Manual Reset

By connecting a push-button directly from MR to

ground, the designer adds manual system reset capa-

bility. The MR pin is LOW while the push-button is

closed and RESET/RESET pin remains HIGH/LOW

after.

MR

System

Reset

Manual

Reset

X40430

RESET