Interfacing ICs

Pin Diagram of 8279

Pin Diagram of 8279: Fig. 14.83 shows functional and pin diagram of 8279. It is a 40 pin device and looking at Fig. 14.83 (a) we can see that these pins are divided in four functional groups : CPU interface Key data Display data Scan CPU Interface Pins: As shown in Fig. 14.83 (a), it …

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Features of Intel 8279 Programmable Keyboard Display Interface

Features of Intel 8279 Programmable Keyboard Display Interface: The Intel 8279 is a general purpose programmable keyboard and display I/O interface device designed for use with Intel microprocessors. The Features of Intel 8279 Programmable Keyboard Display Interface are 1. It provides a scanned interface to a 64-contact key matrix, with two more keys CONTROL and …

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8259 Block Diagram

8259 Block Diagram: Fig. 14.71 shows the internal 8259 Block Diagram. It includes eight blocks : data bus buffer, read/write logic, control logic, three registers (IRR, ISR and IMR), priority resolver, and cascade buffer. Data Bus Buffer: The data bus buffer allows the 8085 to send control words to the 8259A and read a status …

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Operating Modes of 8257

Operating Modes of 8257: The Operating Modes of 8257 can be programmed to operate in following modes : Rotating Priority Mode : In rotating priority mode, the priority of the channels has a circular sequence. In this, channel being serviced gets the lowest priority and the channel next to it gets the highest priority as …

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8257 Pin Diagram

8257 Pin Diagram: Fig. 14.61 shows 8257 Pin Diagram. Data Bus (D0-D7) : These are bi-directional tri-state signals connected to the system data bus. When CPU is having control of system bus it can access contents of address register, status register, mode set register, and a terminal count register and it can also program, control …

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Features of Microprocessor 8257 DMA Controller

Features of Microprocessor 8257 DMA Controller: The Features of Microprocessor 8257 DMA Controller are follows, 1. It is a programmable; 4-channel, direct memory access controller. Each channel can be programmed individually. Therefore, we can interface 4 input/output devices with 8257. 2. Each channel includes a 16-bit DMA address register and a 14-bit counter. DMA address …

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