Browse Prior Art Database

DMA Slave Data Security

IP.com Disclosure Number: IPCOM000108338D
Original Publication Date: 1992-May-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 1 page(s) / 27K

Publishing Venue

IBM

Related People

Arimilli, RK: AUTHOR [+3]

Abstract

Disclosed is a method to achieve data security during DMA slave operations on the Micro Channel*.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 100% of the total text.

DMA Slave Data Security

       Disclosed is a method to achieve data security during DMA
slave operations on the Micro Channel*.

      During a DMA slave operation, data is transferred between
memory and the DMA slave.  Memory can be mapped either to system
memory or memory on the Micro Channel. During transfers between Micro
Channel memory and the DMA slave, data is temporarily stored in a
buffer.  This buffer may contain data from a previous operation.
Normally, all four bytes are driven on the Micro Channel even if the
data to be transferred is a single byte as indicated by the Micro
Channel signals.  In this case, data from the previous operation
would get propagated on the Micro Channel presenting a security
exposure.

      This data security exposure is resolved by driving only valid
data during the current DMA slave operation.  This is achieved
without performance degradation.  The system then becomes tolerant to
hostile devices and programmers.
*  Trademark of IBM Corp.