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INPUT AND OUTPUT (1/0) DEVICES

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INPUT AND OUTPUT (1/0) DEVICES Input/Output devices are the means through which the MPU communicates with "the outside world." The MPU accepts binary data as input from devices such as keyboards and analog-to-digital (A/D) converters and sends data to output devices such as LEDs or printers. There are two different methods b which an MPU can identify I/O devices :one uses an 8-bit address and the other a 16- bit address These methods are described briefly in the following sections. I/Os with 8-Bit Addresses (Peripheral-Mapped I/O) In this type of I/O, the MPU uses eight address lines to identify an input or an output device; this is also known as peripheral-mapped I/O .The eight address lines can have 256 (28 combinations) a dresses ;thus the MPU can identify 256 input devices and 256 output devices with addresses ranging from 00 H to FF H · The input and output devices are differentiated by the control signals I/O Read for input devices and I/O Write for output device...
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Counters and Timers

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Counters and Timers Many microcontroller applications require the counting of external events, such as the frequency of a pulse train, or the generation of precise internal time delays between com­puter actions. Both of these tasks can be accomplished using software techniques, but software loops for counting or timing keep the processor occupied so that other, perhaps more important, functions are not done. To relieve the processor of this burden, two 16-bit up counters, named T0 and T1, are provided for the general use of the programmer. Each counter may be programmed to count internal clock pulses, acting as a timer, or pro­grammed to count external pulses as a counter. Bit Symbol Function 0 IT0 External interrupt 0 signal type control bit. Set to 1 by program to enable external interrupt...
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Computer Processors and Support:IEEE754 Floating Point Numbers and Memory Types

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Computer Processors and Support I’m sure that you realize that computer processors are really just a great big sequential circuit, but I’m sure that you have no idea where to start understanding how they work. Traditional computer processors are designed using a selection of six or so basic design philosophies that give them different characteristics. In this chapter, I will introduce you to the different issues that have to be confronted in designing computer processors, along with some of the technologies that have been developed to support them. From a high level, computer processor architects choose from making the processors ‘‘RISC’’ (‘‘Reduced Instruction Set Computers’’ – pronounced ‘‘risk’’) based or ‘‘CISC’’ (‘‘Complex Instruction Set Computers’’) based. CISC processors tend to have a large number of instructions, each carrying out a different permutation of the same operation (accessing data directly, through index registers, etc.) with instructions perceived to be usefu...
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