Browse Prior Art Database

Direct Memory Access Mapping Mechanism for Enhanced Capabilities Port

IP.com Disclosure Number: IPCOM000117720D
Original Publication Date: 1996-May-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 52K

Publishing Venue

IBM

Related People

Bland, PM: AUTHOR [+6]

Abstract

Disclosed is a method for routing a single Enhanced Capabilities Port (ECP) channel REQ/ACK pair to a number of different ISA compatible DMA channels. The routing is dynamic and under software control. One purpose of this invention is to add flexibility to ISA systems in an effort to avoid ECP conflicts with other devices or adapters in the system. The second purpose is to make the configuration of the system more user friendly by providing software control, rather than hardware configuration jumpers.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Direct Memory Access Mapping Mechanism for Enhanced Capabilities Port

      Disclosed is a method for routing a single Enhanced
Capabilities Port (ECP) channel REQ/ACK pair to a number of different
ISA compatible DMA channels.  The routing is dynamic and under
software control.  One purpose of this invention is to add
flexibility to ISA systems in an effort to avoid ECP conflicts with
other devices or adapters in the system.  The second purpose is to
make the configuration  of the system more user friendly by providing
software control, rather  than hardware configuration jumpers.

      This invention allows DMA resources to be 'mapped' to one of
several states in the system, freeing up additional channels and
avoiding conflicts.  This is accomplished by providing a hardware
register which is programmed by engineering software (or SMIT, or
other configuration utility).  The user or configuration utility can
pick which DMA channels are allocated to specific functions, or
choose not to assign any DMA channels to a specific function.

      This invention describes logic to map the DMA channel allocated
for the Enhanced Capabilities Port (ECP) to one of several channels
(or none).  The logic is controlled through an I/O register located
at address port 081Ch and is setup by a utility in the System
Management Services (SMS) program located in the boot ROM.  The
register implementation is described in the section below.
Basically, the three least significant bits in the regis...