THE MAGAZINE FOR COMPUTER APPLICATIONS
Circuit Cellar Online offers articles illustrating creative solutions
and unique applications through complete projects, practical
tutorials, and useful design techniques.

WORKING WITH A LITTLE EE

by George Martin

Start • The Basics • Getting the Routine Down • Debugging Your Reads and Writes • Sources

GETTING THE ROUTINE DOWN

At a quick glance, it's encouraging to be able to write just a few routines to manage the device. Table 1 extracts some of the routines developed in EEmem.c.

These are basic bit operations, which can be built into larger functions. If you check out the datasheet (www.microchip.com), there are some timing requirements to consider.

Clock high (min): 4000 ns
Clock low (min): 4700 ns
Output valid from clock (max): 3500 ns
Bus free time (min): 4700 ns

The EE memory I'm writing about has a vintage 1995 datasheet. The microprocessor I used is an 80C196, operating at about 10 MHz. As you can see in the code, I don't have to worry about going too fast for the device. Because 1995 is ancient history in today's world of technology, check and double-check your datasheets.

I didn't attempt to streamline these routines in any way. For my project, the EE memory's reads and writes were so infrequent that it wasn't necessary. Also, I reserved a place for a delay routine that wasn’t needed since the microprocessor did not exceed the timing requirements of the EE device.