MCP79401 datasheet(15/38 Pages) MICROCHIP

Part #	MCP79401

Description	I2C??Real-Time Clock/Calendar with SRAM, Unique ID and Battery Switchover

PDF	38 Pages

Scroll/Zoom	100%

Manufacturer	MICROCHIP [Microchip Technology]

Direct Link	http://www.microchip.com

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15 / 38 page

 2011 Microchip Technology Inc.

DS25009A-page 15

MCP7940X

4.2.6

POWER-FAIL TIME-STAMP

The MCP7940X family of RTCC devices feature a

power-fail time-stamp feature. This feature will save

the time at which VCC crosses the VTRIP voltage. To

use this feature, a VBAT supply must be present and

the oscillator must also be running.

There are two separate sets of registers that are used

to record this information:

• The first set located at 0x18h through 0x1Bh are

loaded at the time when VCC fails and the RTCC

operates on the VBAT. The VBAT (register 0x03h

bit 4) bit is also set at this time.

• The second set of registers, located at 0x1Ch

through 0x1Fh, are loaded at the time when VCC

is restored and the RTCC switches to VCC.

The power-fail time-stamp registers are cleared when

the VBAT bit is cleared in software.

MCP79401 Datasheet(PDF) 15 Page - Microchip Technology