In the last few years, the'51 (and mcus in general) get stuffed with features - mostly analog - such as DAC/ADC, reset generator and brownout detector, watchdog (hopefully with an own oscillator, independent fron the mcu clock). Other extras are the onboad memories - self-programmable FLASH, EEPROM, extended (although still ridiculously little) RAM. Yet another extra very popular today is an integrated support for in-circuit debugging.

The idea behind this strategy is, that although these extra features might not be used in a maybe big portion of the designs (and certainly not all of them), they cost negligible when integrated but if needed, save considerable resources of all kind compared to discrete solution.

I would like to start a discussion, if there is something still missing from common 51s, possibly cheap to implement, even if not often used.

Let me start the list with an externally latchable input register. I am missing it when trying to establish multiprocessor communication via parallel bus, often of a big boy(master)-little boy(slave) type. I am forced to use a discrete latch and a flip-flop (as a flag to the slave that the latch has been written).

An extension to this idea would be an address+multiple data register scheme, similar to that used in parallel interfaced peripherals (e.g. UARTs).

Jan Waclawek

PS. Erik, I hope it was OK to use your favourite expression in the subject.