How many times can you write to the DS3231?

There are no write limitations on the DS3231. We utilize SRAM memory cells, with battery backup to achieve non-volatility. There is no user EEPROM in the DS3231, and so there are no write limitations.

If the I2C access fails on the DS3231, is there any way to recover it?

There is no I2C bus time-out feature in the DS3231. The standard 9 SCL clocks to finish whater commnd the DS3231 things it is executing should allow the DS3231 to release the bus. Power cycling the DS3231 will also reset the control of the I2C bus.

Does the DS3231 provide trickle charging?

The DS3231 does not offer trickle charging. It is ok to use a rechargeable battery, but you need to provide an external trickle charger.

Is the DS3231 accurate outside of the operational temperature range?

The DS3231 operates from -45C to 85C. Beyond those limits, the device runs out of frequency trim range and the timekeeping accuracy degrades drastically from our specified 5ppm limit.

Is the aging register EEPROM or just battery backed CMOS ram?

The aging register of the DS3231 does require a power supply for retaining the value as it is stored in SRAM.

Can the DS3231 use clock stretching in response messages?

The DS3231 does not use clock stretching. During an I2C read, the DS3231 will not implement any stretching of SCL. SCL on this device is an open drain input only structure.

What is the expected ppm accuracy for the DS3231?

We expect +/-3.5ppm accuracy across the operational temperature range of -40C to +85C for the DS3231.

What type of battery should be used with DS3231MPMB1?

DS3231MPMB1 has a BH401 battery holder that can accept cells like CR1025.

What is the DS3231 process?

Answer: The DS3231 process is CMOS.

Do the time and date registers of the DS3231M get reset if I use I2C communications when I am on my backup power source?

No, the time and date registers are only reset upon first reading of the I2C registers after a power source has been applied. If you have two power sources Vcc and Vbatt connected, the time and date registers will not be reset as long as at least one power source satisfies specifications. The time and date registers are only reset when reading them after the internal oscillator has been restarted. The internal oscillator is shut down when all power sources are removed and restarts when a valid power source is applied.

How sensitive is the DS3231 to humidity?

The DS3231 is am MSL level 1 component. Please ensure the parts are stored in an area where the relative humidity remains under 85%.

Is it ok to adjust the aging register often when comparing the DS3231 against another, more accurate source?

Yes, it is ok to tweak the register. The data sheet mentions the aging register comes more effective when there is a change in ambient temperature of the device.

Can I use an external crystal to improve the accuracy of the DS3231?

An external crystal cannot be used with the DS3231 as the DS3231 was not designed with any designated pins for an external crystal.. However, to improve on the DS3231's accuracy and drift specifications the designer can choose their own RTC source and periodically write that data to the DS3231's clock registers to update them. This can be useful in applications where the designer would like to sync multiple RTC's to one clock source or would just like to improve timekeeping accuracy.

What is the recommended pull-up resistor value for the open-drain outputs of the DS3231M?

The recommended pull-up resistor values for the 32KHZ and INT/SQW outputs are between 1kOhm and 10MOhm. The RST pin has an internal pull-up of 50kOhm and no external pull-up should be connected to this pin.

Is there any way to detect a failing external battery before the internal clock stops working?

There is no voltage monitoring of the backup source included with the TCXO components. If the bias falls below minimum operational levels, OSF should become set, but any 'response to a failing battery' while operating on that battery is up to the customer's implementation.

How to get DS3231 alarm on half hour?

1. Enable both Alarm 1 and Alarm 2 Interrupts: set A2IE/A1IE (0Eh) to logic 1. 2. For the Alarm Mask Bits, use “Alarm when minutes match” for both alarm 1 and alarm 2, but the interval for Alarm 1 and 2’s Minutes configuration is 30 minutes.