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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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8086 I/O Ports , Important Points To Be Considered for 8086 Interface to Memory and I/O and 8086-Based Microcomputer

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9.9.3 8086 I/O Ports Devices with 8-bit I/O ports can be connected to either the upper or the lower half of the data bus. If the I/O port chip is connected to the lower half of the 8086 data lines (AD0- AD7), the port addresses will be even (A 0 = 0). On the other hand, the port addresses will be odd (A0 = 1) if the I/O port chip is connected to the upper half of the 8086 data lines (AD8-AD 15 ). A0 will always be 1 or 0 for the partitioned I/O chip. Therefore, A 0 cannot be used as an address input to select registers within a particular I/O chip. If two chips are connected to the lower and upper halves of the 8086 address bus that differ only in A0 (consecutive odd and even addresses), A0 and BH E must be used as conditions of chip select decoding to avoid a write to one I/O chip from erroneously performing a write to the other. The 8086 uses either standard I/O or memory-mapped I/O. The standard I/O uses the instructions IN and OUT, and is able to provide up to 64K bytes of I/...
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8089 I/O Processor

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8089 I/O Processor 1. Dra w the pin connection diagram of 8089. Ans. The pin connection diagram of 8089 is shown in Fig. 19c.1. 2. Dra w the functional block diagram of 8089. Ans. The functional block diagram of 8089 is shown in Fig. 19c.2. 3. Writ e down the characteristic features of 8089. Ans. The characteristic features of 8089 are as follows: z Very high speed DMA capability—I/O to memory, memory to I/O, memory to memory and I/O to I/O. z 1 MB address capability. z iAPX 86, 88 compatible. z Supports local mode and remote mode I/O processing. z Allows mixed interface of 8-and 16-bit peripherals, to 8-and 16-bit processor buses. z Multibus compatible system interface. z Memory based communications with CPU. z Flexible, intelligent DMA functions, including translation, search, word assembly/ disassembly. z Supports two I/O channels. 4. Indicat e the data transfer rate of 8089 IOP. Ans. On each of the two channels of 8089, data can be transferred ...
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