Posts by Farahat

DMA Controller 8257 The Direct Memory Access or DMA mode of data transfer is the fastest amongst all the modes of data transfer. In this mode, the device may transfer data directly to/from memory without any interference from the CPU. The device requests the CPU (through a DMA controller) to hold its data, address and […]
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Command Words of 8259A The command words of 8259A are classified in two groups, viz. initialization command words (ICWs) and operation command words (OCWs)Initialization Command Words (ICWs) Before it starts functioning, the 8259A must be initialized by writing two to four command words into the respective command word registers. These are called as initialization command […]
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Operating Modes of 8253 Each of the three counters of 8253 can be operated in one of the following six modes of operation. 1. Mode0 (Interrupt on terminal count) 2. Model (Programmable monoshot) 3. Mode2 (Rate generator) 4. Mode3 (Square wave generator) 5.Mode4 (Software Triggered robe) 6.Mode5 (Hardware triggerred strobe) In this section, we will […]
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Display Modes There are various options of data display The first one is known as left entry mode or type writer mode. Since in a type writer the first character typed appears at the left-most position, while the subsequent characters appears successively to the right of the first one. The other display format is known […]
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8279 Programmable Keyboard/Display Controller and Interfacing The Keyboard/Display Controller 8279 Intel’s 8279 is a general purpose Keyboard Display controller that simultaneously drives the display of a system and interfaces a Keyboard with the CPU. The Keyboard Display interface scans the Keyboard to identify if any key has been pressed and sends the code of the […]
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Parallel Printer Interface: For the most common printer such as the IBM PC printer, the Epson dot matrix printers and the Panasonic dot matrix printers, data to be printed is sent to the printer as ASCII characters on eight parallel lines. The printer receives the characters to be printed and stores them in an internal […]
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Static Memory Interfacing The general procedure of static memory interfacing with 8086 as follows: 1. Arrange the available memory chips so as to obtain 16-bit data bus width. The upper 8-bit bank is called ‘odd address memory bank’ and the lower 8-bit bank is called ‘even address memory bank’. 2. Connect available memory address lines […]
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INTERFACING ANALOG TO DIGITAL DATA CONVERTERS This topic is aimed at the study of 8-bit and 12-bit analog to digital converters and their interfacing with 8086. In most of the cases, the PIO 8255 is used for interfacing the analog to digital converters with a microprocessor. We have already studied 8255 interfacing with 8086 as […]
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6.1 8255 Programmable Peripheral Interface and Interfacing The 8255 is a widely used, programmable parallel I/O device. It can be programmed to transfer data under data under various conditions, from simple I/O to interrupt I/O. It is flexible, versatile and economical (when multiple I/O ports are required). It is an important general purpose I/O device […]
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Interfacing Devices Memory Devices and Interfacing Interfacing Devices Any application of a microprocessor based system requires the transfer of data between external circuitry to the microprocessor and microprocessor to the external circuitry. Most of the peripheral devices are designed and interfaced with a CPU either to enable it to communicate with the user or an […]
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