Browse Prior Art Database

Direct Access Method

IP.com Disclosure Number: IPCOM000042841D
Original Publication Date: 1984-Jun-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Herring, LC: AUTHOR [+2]

Abstract

This article describes a technique which allows data from a microprocessor RAM (random-access memory) to be transferred directly to an output device. The microprocessor executes a single instruction to effectuate data transfer. The drawing shows a graphic representation of the technique which has the following steps: (1) The processor 10 enables the direct transfer circuits (not shown by a signal from an output port (not shown). (2) A read instruction is next executed by the processor. The instruction (a) activates the RAM address bus, and (b) generates the control signals to transfer the data from RAM to the processor. These control signals also cause the data to be transferred to the output device.

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Direct Access Method

This article describes a technique which allows data from a microprocessor RAM (random-access memory) to be transferred directly to an output device. The microprocessor executes a single instruction to effectuate data transfer. The drawing shows a graphic representation of the technique which has the following steps: (1) The processor 10 enables the direct transfer circuits (not shown by a signal from an output port (not shown). (2) A read instruction is next executed by the processor. The instruction (a) activates the RAM address bus, and (b) generates the control signals to transfer the data from RAM to the processor. These control signals also cause the data to be transferred to the output device. An AND circuit 12 combines control signals from the processor to form the strobe signal which gates the data into the output device. Following the transfer of data, the processor executes step 3, namely, the processor disables the direct transfer circuits. Because only one instruction is executed, the access time for data from the RAM to the output device is much faster than a multiple instruction technique wherein the data is transferred from the RAM into the processor and is read out from the processor into the output device.

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