Hi Stefan, Jan and Andy,

Thanks for your patient and helpful replies to my AT89C51RD2 update query.

Yes, the 68-pin PLCC IE2 model mentioned on the Keil, and a handful of other, web sites did spark my interest, Jan. You're correct in identifying this as misleading information, as only unwieldy emulation hardware seems to currently exist for this apparently forthcoming product.

Stefan, its really only the 1769-byte XRAM limitation of my current Atmel AT89C51RD2 that is holding me back. Any additional enhancements beyond the more expansive XDATA space may be a plus, provided drop-in pin compatibility with the RD2 was not compromised.

Well your suggestion of incorporating some serial ram got me thinking, Stefan. The RD2 seems to have hardware SPI functionality that might be used for this purpose, but the interfacing job may be a little too fiddly for those, which it is intended.

The Ethernet enabled control board in question does have space for an I2C controlled RTC, as well as for 4 x individually hardwire-addressed 8-pin sockets for I2C EEROM chips. The SRAM suggestion got me thinking about this low-speed option, and it appears that any I2C RTC might offer the first 56-bytes of NV-RAM expansion. Following Andy's helpful suggestion concerning IC stockist's parametric search offerings, I went on a subsequently very efficient search for SRAM chips to possibly fill the other 4 x 8-pin I2C sockets. Unfortunately, it appears that the 256 x 8-bit PCF8570 static RAM offering from Phillips may be the largest available in it's class.

Hmm...this all brought to mind an experience I had recently during a job interview with a professional embedded software engineer. After proudly boasting of what I thought were my enviable accomplishments in managing to wring big functionality from little processors, I was disappointed to have been (correctly) instructed that "nah, we'd use an ARM for that".

Well, maybe if I have reached the limits of what I at least can manage with constricted 8051 style hardware, then maybe my fascination with the little 8051 Ethernet controller board I have been using is no longer appropriate. ARM based boards are better value and seem to offer quality open sourced development tools, as well as lots of open sourced software projects. Hmm...maybe I should stop messing about with all this round-robin and interrupt driven nonsense, and start thinking about graduating to a real-time OS enabled and more generously resourced architecture?

Regards,
Murray R. Van Luyn.