It is a Harvard architecture, single chip micro controller series which was developed by intel in 1980 for use in embedded systems.
one particularly useful featureof 80c51 core was the inclusion of a boolean( 布尔数学体系的)processing engine which allows bit-level boolean logic operations to be carried out directly and efficiently
on select internal registers and select RAM locations.
This advantageous feature helped cement the 80c51's popularity in industrial control applications because it reduced code size by as much as 30%.
Another valued feature is the inclusion of four bank selectable working register sets which greatly reduce the amount of time required to complete an interrupt service routine.
With a single instruction the 8051 can switch register banks as opposed to the time consuming task of transferring the critical registers to the stack or designated RAM locations. These registers also allowed the 8051 to quickly perform a context switch which
is essential for time sensitive real-time applications.
Features of the modern 8051include built-in reset timers with brown-out detection, on-chip oscillators, self-programmable Flash ROM program memory, built-in external
RAM, extra internal program storage, bootloader code in ROM, EEPROM non-volatile data storage, I2C, SPI, and USB host interface, CAN or LIN bus, PWM generators, analog comparators, A/D and D/A converters, RCTS, extra counters and timers, in-circuit debugging
facilities, more interrupt sources, and extra power saving modes.
TIPS：
Bank switching can be considered a way of extending the address bus of a processor with some external register. For example, a processor with a 16-bit external address bus can only address 216 = 65536 memory locations. If an external latch
was added to the system, it could be used to control which of two sets of memory devices, each with 65536 addresses, could be accessed. The processor could change which set is in current use by setting or clearing the latch bit.