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FM3130 Integrated RTC/Alarm with 64Kb FRAM

Rev. 3.2

Sept. 2011

Page 2 of 22

Figure 1. Block Diagram

Pin Descriptions

Pin Name

Type

Pin Description

X1, X2

I/O

32.768 kHz crystal connection. When using an external oscillator, apply the clock to X1

and a DC mid-level to X2 (see Crystal Type section for suggestions).

ACS

Output

Alarm/Calibration/SquareWave: This is an open-drain output that requires an external

pullup resistor. The alarm, calibration, and square wave functions all share this output.

In Alarm mode, this pin acts as the active-low alarm output. In Calibration mode, a 512

Hz square-wave is driven out. In SquareWave mode, the user may select a frequency of

1, 512, 4096, or 32768 Hz to be used as a continuous output. Refer to Table 3. Control

Bit Settings for ACS Pin to determine the bit settings for each mode.

SDA

I/O

Serial Data & Address: This is a bi-directional line for the two-wire interface. It is

open-drain and is intended to be wire-OR‟d with other devices on the two-wire bus. The

input buffer incorporates a Schmitt trigger for noise immunity and the output driver

includes slope control for falling edges. A pull-up resistor is required.

SCL

Input

Serial Clock: The serial clock line for the two-wire interface. Data is clocked out of the

part on the falling edge, and data into the device on the rising edge. The SCL input also

incorporates a Schmitt trigger input for noise immunity.

VBAK

Supply

Backup supply voltage: A 3V battery or a large value capacitor. If no backup supply is

excessive current when using a lithium battery.

VDD

Supply

Supply Voltage.

VSS

Supply

Ground

F-RAM

Array

2-Wire

Interface

RTC

-

+

RTC Registers

Special

Function

Registers

X1

X2

LockOut

Switched Power

RTC Cal.

Battery Backed

Nonvolatile

ACS

Alarm

512Hz/SQW

Alarm

SCL

SDA

VDD

VBAK