My choice is not MCS-51 parts. Intel stopped making those years ago. Instead I use the SiLabs C8051Fxxx series parts. These are assembly language compatible with the original MCS-51 parts from Intel but better in almost every regard over the old parts.

Over the years I have used MCUs from Motorola, Freescale, Philips, Atmel AVR, Hitachi, Renasas, Zilog, Microchip and Cypress (plus others I have most assuredly forgotten about). I keep coming back to the SiLabs parts because of ability to re-use code from previous projects. Nothing is better than to attack a new project with a slew of known good code modules so that you can hit the ground running. These days, in the fast world where we live, there is rarely the opportunity to be able to be paid to learn the foibles of a new MCU family that you are not yet familiar with. On top of that the cost of professional grade tools for MCUs is often 1000's of $$ and one wants to leverage that investment as much as possible.

It has been my experience over and over again in many years though that, despite what I said above, when facing the need to address for pay work it is a huge advantage to be a seasoned MCU development professional. A huge amount of the techniques for development, coding, debugging and deployment are the same regardless of what MCU family you are setting out to use. What this means is that applying different MCU parts means learning how to deal with the foibles as I alluded to above. Sometimes that means having to dive in with both feet and work double hard to debug and get a new product working.

I have found that as I get older I have less energy to deal with foibles and so like to leverage my experience base. That means that I come first back to the SiLabs C8051Fxxx family.

Michael Karas