memory interfacing in 8085 microprocessor pdf

package and requires a single +5V supply for its operation and allows up to four I/O devices to be interfaced to the microprocessor. It is a 4-channel programmable direct memory access controller. The Intel 8257 is a programmable DMA controller. In DMA transfer scheme, data are directly transferred from I/O devices to RAM or from RAM to I/O device.

8257 (DMA Controller) - Direct Memory Access (DMA) is an I/O technique commonly used for high-speed data transfer.

A0: This address line acts in conjunction with RD, WR, CS to interrupt command words CPU writes and status the CPU wants to read.

IR0-IR7: These lines are used for interrupt requests.

INT: This line is used to interrupt microprocessor.

When signal on this pin is low, 8259 sends various status on the data bus for processor. When signal is low, 8259 accepts command word from microprocessor. This signal enables the chip to perform various functions. 8259 can work in fully nested mode, automatic rotation and specific rotation mode. including pins related to data bus, buffer, three registers (IRR, ISR and IMR), cascade buffer (cas 0, cas 1, and cas 2), priority resolver, control logic and Read/ Write logic.

8259 (Programmer Interrupt Controller) - It is a 28 pin I.C.

This unit consists of study of various microprocessor chips along with their pin description, architectural diagram, their features and their applications.

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Memory interfacing in 8085 microprocessor pdf