[SOLVED] ds1307 doesnot run when disconnected from vcc

avirajose said:

I have sucessfully interfaced ds1307 with pic16f877a and is working fine. But it only starts its oscillation when in vcc only. When i disconnect the vcc ,it stops the oscillation and simply store the previous date.
can anyone suggest me a solutionb for it.

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The DS1307 has a built-in power-sense circuit that detects power failures and automatically switches to the backup supply. Timekeeping operation continues while the part operates from the backup supply.

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Vbat:

Backup Supply Input for Any Standard 3V Lithium Cell or Other Energy Source. Battery voltage must be held between the minimum and maximum limits for proper operation. Diodes in series between the battery and the VBAT pin may prevent proper operation. If a backup supply is not required, VBAT must be grounded. The nominal power-fail trip point (VPF) voltage at which access to the RTC and user RAM is denied is set by the internal circuitry as 1.25 x VBAT nominal. A lithium battery with 48mAh or greater will back up the DS1307 for more than 10 years in the absence of power at +25°C.

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rajudp said:

check the data sheet there is a bit to enable oscillation i thing it is at address 0 in SEC reg

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