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Let’s start by looking at a system. Microprocessor ( µ p) This is the device that you buy: just an integrated circuit as in Figure 1.6. On its own, without a surrounding circuit and applied voltages it is quite useless. It will just lie on your workbench staring back at you.
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Microprocessor (µp) • This is the device that you buy: just an integrated circuit as in Figure 1.6. On its own, without a surrounding circuit and applied voltages it is quite useless. It will just lie on your workbench staring back at you. • Microprocessor-based system • This is any system that contains a microprocessor, and does not necessarily have anything to do with computing. In fact, despite all the hype, computers use only a small proportion of all the microprocessors manufactured. • Our garage door opening system is a microprocessor-based system or is sometimes called a microprocessorcontrolled system.
Microcomputer • The particular microprocessor-based systems that happen to be used as a computer are called microcomputers. The additional circuits required for a computer can be built into the same integrated circuit giving rise to a single chip microcomputer. • Microcontroller • This is a complete microprocessor-based control system built onto a single chip. It is small and convenient but doesn’t do anything that could not be done with a microprocessor and a few additional components.
MPU and CPU • An MPU is a MicroProcessor Unit or microprocessor. • A CPU is a Central Processing Unit. This is the central ‘brain’ of a computer and Introduction to Microprocessors and Microcontrollers can be (usually is) made from one or more microprocessors. • The IBM design for the ‘Blue Gene’ supercomputer includes a million processors! • Remember: • MPU is the thing • CPU is the job
Microprocessor (MPU) A group of electronic circuits fabricated on a semiconductor chip that can read binary instructions written in memory and process binary data according to those instructions CPU and MPU 7
Bits, bytes and other things • Nibble • A group of four bits handled as a single lump. It is half a byte. • Byte • A byte is simply a collection of 8 bits. Whether they are ones or zeros or what their purpose is does not matter.
Word A number of bits can be collected together to form a ‘word’. Unlike a byte, a word does not have a fixed number of bits in it. The length of the word or the number of bits in the word depends on the microprocessor being used.
Long word In some microprocessors where a word is taken to mean say 16 bits, a long word would mean a group of twice the normal length, in this case 32 bits.
Kilobyte (Kb or KB or kbyte) • A kilobyte is 1024 or 210 bytes. In normal use, kilo means 1000 so a kilovolt or kV is exactly 1000 volts. In the binary system, the nearest column value to 1000 is 1024 since 29 = 512 and 210 = 1024.
The difference between 1000 and 1024 is fairly slight when we have only 1 or 2 kB and the difference is easily ignored. However, as the numbers increase, so does the difference. The actual number of bytes in 42 kB is actually 43 008 bytes (42 1024).
Megabyte (MB or Mb) • This is a kilokilobyte or 1024 1024 bytes. Numerically this is 220 or 1 048 576 bytes. Be careful not to confuse this with mega as in megavolts (MV) which is exactly one million (106).
Gigabyte (Gb) • This is 1024 megabytes which is 230 or 1 073 741 824 bytes. In general engineering, giga means one thousand million (109). • Terabyte (TB or Tb) • Terabyte is a megamegabyte or 240 or 1 099 511 600 000 bytes (Tera = 1012).
Petabyte (PB or Pb) • This is a thousand (or 1024) times larger than the Terabyte so it is 1015 in round numbers or 240 which is pretty big. If you are really interested, you can multiply it out yourself by multiplying the TB figure by 1024.
