Atmel’s AVR is most interesting chip, with modern 8-bit RISC MCU and rich I/O performance in less $ price. With tons of document available on web since simple D.I.Y. hardware project to complex system design.
AVR becomes the value choice for implement “Physical Computing” idea. The proposal of “physical Computing ” is made for interaction of hardware control “the real world” with easy software programming.
MIDE-51 software package on web with ASEM-51 Assemmbler tools for MCS-51 beginner.
MCS-51 is the good MCU for getting start to learn and use. But now.. we have many microcontroller available on market. Modern chips had much more advantage features than old MCS-51 , e.g. Microchip’s PIC / dsPIC, Atmel AVR / AVR32 thru high-end ARM base MCU”