This made them more suitable for battery-powered devices. MCS-8051 projects with circuit diagram and source code pdf family of binary compatible microcontrollers. With one instruction, the 8051 can switch register banks versus the time consuming task of transferring the critical registers to the stack, or designated RAM locations.
The main program then performs serial reads and writes simply by reading and writing 8-bit data to stacks. External RAM and ROM share the data and address buses. The original 8051 core ran at 12 clock cycles per machine cycle, with most instructions executing in one or two machine cycles. 8051 could thus execute 1 million one-cycle instructions per second or 500,000 two-cycle instructions per second. Enhanced 8051 cores are now commonly used which run at six, four, two, or even one clock per machine cycle, and have clock frequencies of up to 100 MHz, and are thus capable of an even greater number of instructions per second. Dallas and a few Atmel devices have single cycle cores. ROM, capable of running user programs loaded into RAM.
MCS-51 based microcontrollers have been adapted to extreme environments. MCS-51 microcontrollers for use in spacecraft are available e. In some engineering schools the 8051 microcontroller is used in introductory microcontroller courses. 8051 is the original name by Intel with 4 KiB ROM and 128 byte RAM. Variants starting with 87 have a user programmable EPROM memory, sometimes UV erasable. 8031 and 8032 are ROM-less versions, with 128 and 256 bytes RAM. The last digit can indicate memory size, e.