Embedded Systems Lesson 5 (Embedded Processors) PDF

Embedded Systems Lesson 5 (Embedded Processors) General Purpose Processors designed to solve problems in a large variety of applications manufacturer can invest more for improving the design with advanced features design tools are provided...

Embedded Systems Lesson 5 (Embedded Processors) General Purpose Processors designed to solve problems in a large variety of applications manufacturer can invest more for improving the design with advanced features design tools are provided by the manufacturer in such processors microprocessor is a clock driven semiconductor device Microprocessors consists of following three building blocks: 1. Arithmetic and Logic Unit (ALU): a. constructed with logic gates b. used for mathematical computation and logical decision  2. Register Array: a. consist of memory elements fabricated in microprocessor. b. microprocessors are named according to its register size c. store data temporarily during execution of the program d. program counter (PC), holds the address of the next program instruction e. Instruction register (IR) to hold the fetched instruction 3. Control Unit (CU): a. provides control signal to different segments of microprocessor b. controls the timing of operation of electronic circuits of microprocessor. c. consists of circuitry for retrieving program instructions and moving data through the data-path according to those instructions Embedded Microprocessor VLSI chips that are incorporated into products  microprocessors that are used in electronic devices designed to perform a certain task and the user seldom has to interact with it Two areas of embedded control applications: 1. Event control or real-time control 2. Data control microcontrollers are used for event control or real-time control embedded microprocessors are used for data control Embedded controller require following building blocks: 1. Data processing unit 2. Data formatting unit 3. I/O control unit 4. Direct memory access (DMA) control unit 5. Memory 6. CPU 7. Timer unit. Characteristics of Embedded Microprocessors does not require any human interaction, no need of human supervisor relies on the stored programs and data being sent to control its behavior interact with their environments through an interrupt system interrupts are signals sent from devices that let the processor know that they need to use the processor processor then enters its interrupt program and decodes the source to take the correct action programs are stored in memory does not possess a large amounts of available memory programs run by embedded microprocessors are usually short use a variety of other devices which are built onto the chip as well they sometimes need to accept input from the device through the analog to digital converter analog to digital converter is used to convert incoming analog signal into data form that the processor can recognize digital to analog converter allows the processor to send signal to the device it is controlling most common types of timer is the Programmable Interval Timer (PIT) counts down from some prefixed value to zero, sends an interrupt to the processor useful to restart the device to be controlled time processing unit (TPU), a timer, more sophisticated in performance can detect input events and generate output events Embedded Microprocessor Systems main function is to monitor and control some real world event Steps to design an embedded microprocessor system : 1. Product requirement definitions 2. Functionality description 3. Processor selection 4. Hardware design 5. Firmware design; 6. Integration steps are not necessarily serial building hardware, writing code, and debugging the system are necessary state transition diagrams in addition to flow charts for design consideration are preferred state and dataflow diagrams are to be made debugging hardware and software is important to consider so that debug facilities can easily be added ARCHITECTURE OF INTEL 80186/80188 MICROPROCESSORS Difference between 80186 and 80188:  1. 80186 microprocessor has 16 bit data bus, while 80188 contains an 8 bit data bus 2. 80186 microprocessor has 6 byte pre-fetch queue but Intel 80188 microprocessor has 4 byte queue. both contain additional reserved interrupt vectors and some powerful built in I/O features Special features:  1. DMA controller unit a. transfers data between I/O and memory 2. three programmable timers a. 16 bit timer/counters b. 2 of the timers are used for following purposes i. Counting external events ii. provide waveforms from either an external clock or a CPU clock iii. interrupt CPU after specified number of events c. third timer counts CPU clock cycles d. can also be used to interrupt CPU after selected clock cycle e. provides a DMA request pulse to the DMA unit 3. Programmable interrupt controller a. provides interrupt requests between internal and external sources b. interrupt, method of creating a temporary halt during program execution i. allows peripheral devices to access the microprocessor  ii. microprocessor responds ISR (Interrupt Service Routine), a short program to instruct the microprocessor on how to handle the interrupt c. 2 interrupt controller chips 8259A can also be cascaded with the integrated interrupt controller of 80186 d. interrupt controller performs the function of master controller