I mostly work in software and not good in reading Hardware data sheets.

I need help in understanding the similarities between RTC DS1374 and RTC DS1307,From below link I could make out that both share the same address on I2C bus and have same set of registers but still few doubts would like to ask.


1) Do both DS1307 and DS1374 have exactly same copy of register set?

2). Do both stores times as year-month-day-hours-minutes-seconds?

3). Do both have have their registers mapped to NVRAM of equal size?

How much DS1307 code can be reused on DS1374?

Any comment would be useful.



These two parts are dissimilar in many many ways.

The block diagrams alone tell much of the story.

DS1374 enter image description here

DS1307 enter image description here

Similarities are limited to the basic functionality of the I/O pins:

  • X1
  • X2
  • VCC
  • GND
  • SCL
  • SDA
  • SQW

Internally the parts diverge greatly.

The '1374 simply uses a 32-bit counter to keep track of the passage of seconds. The software that reads the counter has to translate the count into the normal clock date/time components. On the other hand the '1307 keeps track of the individual date/time components as BCD (binary coded decimal) values in individual registers.

Beyond the basic RTC features the '1374 offers a 24-bit counter that can serve as a WDT (watch dog timer) with an interrupt output and a reset output.

On the other hand the '1307 offers 56 bytes of battery backed up RAM for user data.

In a simple nutshell - you cannot use common software to support these two parts. The register maps are completely different.

  • \$\begingroup\$ Thank @Michael for your Detailed response.Also,would you point me to other RTC's which uses 32 bit counter to keep track of passage of seconds or operates much in the same as DS1374? \$\endgroup\$ – Amit Singh Tomar Sep 27 '14 at 10:55
  • \$\begingroup\$ The only other part that I know of that operates similar to the DS1374 is the DS1672. It lacks the Int/Sqw pin functions but it does offer time storeage in 32-bit seconds format where your software has to convert the 32-bit value into the standard date/time components. See data sheet here: mouser.com/ds/2/256/DS1672-27508.pdf \$\endgroup\$ – Michael Karas Sep 27 '14 at 11:08
  • \$\begingroup\$ One little doubt I have regarding the TOD registers in DS1374 which is four in number,is it there to store seconds,minutes,Hours and date? \$\endgroup\$ – Amit Singh Tomar Sep 28 '14 at 14:40
  • \$\begingroup\$ @AmitSinghTomar - Please understand that the four byte counter in the DS1374 is a simple counter that you pre-load with some starting value. All the RTC does is simply increment this counter once per second. The counter thus allows the recording of the number of seconds that has passed by. The standard technique is to let 0x0000.0000 in this counter represent some known data/time in the past. Then the counter gives you the number of seconds till the current time. Software is then used convert total seconds passed since the past reference date to the current date/time. (continued) \$\endgroup\$ – Michael Karas Sep 28 '14 at 15:10
  • \$\begingroup\$ (continued from above) There are numerous references you can find online regarding how this is done and what past date/time is commonly used as the reference date. The use of a 32-bit seconds counter allows representation of time over a period of approximately 136 years from the reference data. \$\endgroup\$ – Michael Karas Sep 28 '14 at 15:25

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