Pocket Watch 2012

mcp79xx_real_time_clock

I try to spend a few minutes each day looking around the internet for cool or interesting ICs that might be of interest to Solutions Cubed, LLC.  It’s partly a function of my innate nerdom.  Microchip is one company whose parts I enjoy taking a look at (as is Infineon).  This morning I ran across a family of parts that Microchip has expanded; their real-time clock /calendar family.  It took me back to the days of yore when Solutions Cubed was but a wee company.

The MCP794xx (I2C interface) and MCP795xx (SPI interface) provide real time clock functions and the least expensive part is $0.45US / 1000 units (datasheet).   I remember back in the late 1990’s Microchip introduce their PIC12c series of cheap 8-pin microcontrollers.  We were working on a line of miniature engineering modules and designed a real time clock around the PIC12C508.  There was the Pocket Watch A, and then the Pocket Watch B.  This was a serial real time clock with built in alarms and other awesomeness.

As a product it sold okay.  Other real-time clocks on the market at the time were not that cheap, or not that easy to use.  Eventually Dallas Semiconductor (now owned by Maxim, and not the men’s magazine, although that would be funny) came out with a line  of real time clocks.  The demise of the Pocket Watch was imminent.  I still remember sitting at the lab bench tuning the Pocket Watch’s special trim capacitor with a non-ferrous tool.

As an interesting aside, one day I was thumbing through a product brochure Maxim used to mail out and came across a photo of our Pocket Watch B.  They copied it from a print ad we were running and used it to show off a new package style one of their parts had, even though the part on our board was not theirs.  We were incensed!!!!  By the way I stole the image above from Microchip’s web site, but I don’t think they’ll mind.

Back to business… the Microchip real-time clocks have seconds, minutes, hour, day, day of  week, month and year.  They’re even Y2K compatible, imagine that.  Y3K?  They have automatic battery back-up, unique ID’s, internal calibration (as opposed to a sweet tuning capacitor).  Here’s a blurb from the data sheet on some other stuff…

”The clock/calendar automatically adjusts for months with fewer than 31 days, including corrections for leap years. The clock operates in either the 24-hour or 12-hour format with an AM/PM indicator and settable alarm(s) to the second, minute, hour, day of the week, date or month. Using the programmable CLKOUT, frequencies of 32.768, 8.192 and 4.096 kHz and 1 Hz can be generated from the external crystal.”

Anywho, I thought I’d pass this on because it took me back a little to the old days, and looks like a good, cheap, and useful part to keep in mind for future designs.

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