True about the I2C or SPI thing, but maxim-ic doesn't do RTC's with integrated crystal or battery with I2C or SPI. I also like the temperature compensated 32KHz crystal-chip from maxim, it has an accuracy of 1 minute a year, and the frequency almost doesn't change when the temperature increases or decreases. Of course, to use this TOCX, an RTC with integrated battery and crystal (which has an accuracy of 1 minute a month) isn't usable anymore. Now I'm having a dillema: should I go for the easy option and take the module with battery and crystal, but doesn't have a high accuracy; or should I go for the bit harder option and take the TOCX with an RTC without battery or crystal, which will be more expensive (I'll have to find a battery, and lithium ones normally cost loads) and more complex (more chips, have to find a battery-holder, ... ). What would you do? (the last option also includes SPI support)
the one you linked me didn't have the oscillator built in, nor the battery, you have to add those, like most RTCs the phillips semiconductor one i gave the number for on page one looks good, thou i've not used one of them myself. The thing is most RTCs have the control circuitry for the battery backup built in (ie when to switch to the cell), often the only external comonents they need is a lithium cell, a crystal, and 2 caps to start oscillation, most of the datasheets tell you which ones to buy!
The DS1687 incorporates the DS1685 chip, a 32.768kHz crystal, and a lithium battery in a complete, self-contained timekeeping module. The entire unit is fully tested at Dallas Semiconductor such that a minimum of 10 years of timekeeping and data retention in the absence of VCC is guaranteed. Yes it does . The DS1687 is the DS1685 with a lithium battery and crystal. You are in fact correct that most RTC's have built-in circuitry to use a (rechargable if wanted) battery or capacitor (with configurable trickle-charge). Maxim's RTC's all have such circuitry. Some RTC's also exist in a module with battery and crystal. In fact, this is a link to all Maxim's RTC's which are avaible in such a module.
I'm starting a project like this too, using the PIC16F84A and DS32kHz... Anyway, did this project ever finish? or did it die? I found schematics for a 4-led binary clock, and code for it... i know how i would modify the schematics, but i have no experience with PIC programming, and i didn't understand a thing of the code... That's where i need some help.. My idea is to have it to start at 00:00, use rb0, rb1 and rb2 for ten hours and ten minutes, rb3, rb4, rb5 and rb6 for hours and minutes. It would show the time when switch in rb7 is activated, first show hours for 2seconds, then minutes for 2seconds, after that turn off the leds. Here's url to it.. http://www.piclist.com/techref/piclist/cheapic/binclock.htm And yes, i live in finland. the only way to get a binary clock would be to order it from the US, and that'd cost a bit too much to a poor student
