In computer architecture, 4-bit integers, memory addresses, or other data units are those that are 4 bits wide. Also, 4-bit CPUand ALU architectures are those that are based on registers, address buses, or data buses of that size. A group of four bits is also called a nibble and has sixteen (24) possible values. Some of the first microprocessors had a 4-bit word length and were developed around 1970. The TMS 1000, the world’s first single-chip microprocessor, was a 4-bit CPU; it had a Harvard architecture, with an on-chip instruction ROM, 8-bit-wide instructions and an on-chip data RAM with 4-bit words. The first commercial microprocessor was the binary coded decimal(BCD-based) Intel 4004, developed for calculator applications in 1971; it had a 4-bit word length, but had 8-bit instructions and 12-bit addresses.
An 8 bit microcontroller is a self-contained system with memory, a processor and peripherals that can be used as an embedded system. Most programmable 8 bit microcontrollers that are in use today are embedded in other machinery or consumer products including telephones, automobiles, household appliances as well as peripherals for computer systems. Therefore, another name for an 8 bit microcontroller is “embedded 8 bit controller.”When you are looking for the right 8 bit microcontrollers, with the parametric search, you can filter the results by various attributes: by RAM size (128 B, 256 B, 512 B, 768 B, 1 kB), ROM size (4 kB, 8 kB, 16 kB, 32 kB, 64 kB ), number of input lines (from 2 to 100 lines), speed (8 MHz, 20 MHz, 40 MHz, 48 MHz, 50 GHz) and supply voltage (up to 64V).
A 16-bit microprocessor is a faster type of microprocessor. This type of computer hardware processes digital data up to 16 bits in size at once. A 16-bit microprocessor is (generally) faster than an 8-bit microprocessor because it handles 16-bits at a time instead of 8-bits at a time. The biggest and most beneficial thing is the processor speed increase between the two units. The more speed one can obtain the better computer power can be drawn from the computer that uses it. The data transfer rate into and out of memory is doubled and the processing to handle multiple precision data is (approximately) halved. The 16-bit microprocessor also (usually) has more advanced instructions that can do more than the 8-bit microprocessor. 16 bit microcontrollers have evolved to solve high speed control prpblems of the type that might typically be confronted in the control of servo mechanisms such as robot arms or dsp applications.
One of the first 32 bit CPUs — the MC68008 — had registers that held 32 bits, a 20 bit address bus, and an 8 bit data bus. Some popular 32 bit CPUs — i.e., CPUs with registers that hold 32 bits — had a 32 bit data bus and a 24 bit address bus. 32-bit is the word of the day. With a 32-bit program counter you can address 4GByte. ARM is a popular 32-bit controller. There are dozens of manufacturers offering ARMs is all sizes. They’re powerful controllers often having lots of special functions on board, like USB or complete LCD display drivers. ARMs often require large packages, either to accomodate for a large die with a lot of Flash, or because the different functions require a lot of I/O pins. But this package illustrates the possibilities ARM offers.Crossing the boundry from 16 to 32bit involves more than merely doubling the word size of computer. Software boundaries that seperate dedicated programs from supervisory programs are also breached. 32bit design targets robotics, highly intelligent instrumentations, avionics, image processing, telecommunications.