MCP79411 datasheet(29/60 Pages) MICROCHIP

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DS20002266E-page 29

MCP79410/MCP79411/MCP79412

8.6.1

POWER-DOWN TIME-STAMP

REGISTERS

The MCP7941X family of RTCC devices feature a

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

the time at which VCC crosses the VTRIP voltage and is

shown in Figure 8-6. To use this feature, a VBAT

supply must be present and the oscillator must also be

running. The month through minutes are saved.

There are two separate sets of registers that are used

to record this information:

• The first set, located at 0x18 through 0x1B, is

loaded at the time when VCC falls below VTRIP

and the RTCC operates on the VBAT. The VBAT

(Day register bit 4) bit is also set at this time.

• The second set of registers, located at 0x1C

through 0x1F, is 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 (Day register bit 4) bit is cleared in software.

Only the first power-down and power-up time-stamps

are saved by the RTCC.

FIGURE 8-6:

POWER-FAIL GRAPH

VCC

VTRIP(max)

VTRIP(min)

Power-Down

Power-Up

Time Stamp

Note:

It is strongly recommended that the time saver function only be used when the oscillator is running. This

will ensure accurate functionality.

MCP79411 Datasheet(PDF) 29 Page - Microchip Technology