Microprocessors

1. Microprocessors • For a microprocessor to give a working microcomputer system, which can be used for control tasks, additional chips are necessary, e.g. memory devices for program and data storage and input/output ports to allow it to communicate with the external world and receive signals from it.

2. Microprocessors .. • A microcomputer, such as the IBM PC or Apple Macintosh incorporates a microprocessor with the ROM, RAM and interface circuitry requiring many integrated circuits and does not use microcontrollers. • Microcontroller mostly found in small applications carrying out control-oriented activities. It reduces the design to the minimum number of components.

3. Microcontrollers • The microcontroller is the integration of a microprocessor with memory and input/output interfaces, and other peripherals such as timers, on a single chip. • Microcontroller have limited amounts ROM and RAM and are essentially used for the ‘control’ of input/output devices whereas a microprocessor system with separate memory and input/output chips is more suited to ‘processing’ information in computer systems.

4. Microcontrollers • Microcontrollers were developed to meet a need for microprocessors to be put into low-cost products.

5. Microcontrollers • Texas Instruments introduced the TMS-1000 4-bit microcontroller in mid 1970s. • Fairchild introduced the F8, 8-bit microcontroller also in mid 1970s. • Until 1978, Motorola introduced a single chip 6800 and Intel introduced a series of products derived from the 8080 architecture. Both are in current use today

6. Microcontrollers • Today’s microcontroller is a very powerful, low cost and very fast. These microcontrollers often implemented in low-power CMOS. This lets the designer create low-cost battery-operated products. • When compared with a system implemented with a stand-alone microprocessor, microcontroller systems often have less ROM and RAM.

7. Block Diagram of A Microcontroller

8. Basic Structure of a microcontroller • Typically, a microcontroller has:(1) Microprocessor (CPU) (2) Memory RAM, ROM and EPROM or EEPROM (3) Input/Output ports The pins for inputs and outputs are group into units called input/output ports. Usually such ports have eight lines in order to be able to transfer an 8-bit word of data.

9. Input/Output Ports .. • Two ports may be used for a 16-bit word, one to transmit the lower 8 bits and the other the upper 8 bits. The ports can be input only, output only or programmable as either input or output. • Additionally, an input port might be provided with an analog to digital converter as that analog inputs can be easily handled and additionally one port might be for use as a serial port.

10. Input/Output Ports .. • The Motorola 68HC11, Intel 8051 and PIC 16C7x are example of 8-bit microcontrollers, i.e. the data path is 8 bits wide. The Motorola 68HC16 is an example of a 16 bit microcontroller and the Motorola 68300 a 32-bit microcontroller. Family members differ in such features as the combinations of on-chip ROM or EPROM, on-chip RAM and timing facilities.