The Intel MCS-51 (commonly termed 8051) is a single chip microcontroller series
developed by Intel in 1980 for use in embedded systems.
- 8-bit arithmetic logic unit (ALU) and accumulator
- 8-bit registers (one 16-bit register with special move instructions)
- 8-bit data bus and 2×16-bit address buses
- program counter, data pointer
- and related 8/11/16-bit operations
- Boolean processor with 17 instructions
- 1-bit accumulator, 32 registers (4 bit-addressable 8-bit) and up to 144 special 1 bit-addressable RAM variables (18 bit-addressable 8-bit)
- Multiply, divide and compare instructions
- Four fast switchable register banks with eight registers each (memory mapped)
- Fast interrupt with optional register bank switching
- Interrupts and threads with selectable priority
- 128 or 256 bytes of on-chip RAM (IRAM)
- Dual 16-bit address bus; it can access 64 KB (65,536 locations) each of ROM (PMEM) and external RAM (XRAM)
- Four 8-bit bi-directional input/output ports, bit addressable
- UART (serial port)
- Two 16-bit counter/timers