Browse Prior Art Database

Interactive Work Station With Auxiliary Microprocessor for Storage Protection

IP.com Disclosure Number: IPCOM000039105D
Original Publication Date: 1987-Apr-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 5 page(s) / 74K

Publishing Venue

IBM

Related People

Solly, DC: AUTHOR [+3]

Abstract

This article describes an interactive work station in which a microprocessor is used to control various input/output devices and an auxiliary microprocessor is used to provide a storage protection function. Typically, microprocessor-controlled interactive work stations have a microprocessor which controls the various input/output devices, for example, display, printer, keyboard, light pen, communications, etc. Although some control code for the microprocessor will be held in a read only store, control code and data for various tasks will be stored in a read/write or random-access memory (RAM). For a proper functioning of the workstation, it is essential that the various storage locations are not corrupted. Fig.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 24% of the total text.

Page 1 of 5

Interactive Work Station With Auxiliary Microprocessor for Storage Protection

This article describes an interactive work station in which a microprocessor is used to control various input/output devices and an auxiliary microprocessor is used to provide a storage protection function. Typically, microprocessor- controlled interactive work stations have a microprocessor which controls the various input/output devices, for example, display, printer, keyboard, light pen, communications, etc. Although some control code for the microprocessor will be held in a read only store, control code and data for various tasks will be stored in a read/write or random-access memory (RAM). For a proper functioning of the workstation, it is essential that the various storage locations are not corrupted. Fig. 1 is a simplified block diagram of a prior-art interactive workstation comprising a microprocessor 1 having data (d) and address (a) busses 2 and 3, respectively. Various input/output devices, represented symbolically at 4, are connected to the data and address busses 2 and 3 and, also, to an interrupt (i) line 5. Typically, the input/ output devices include a keyboard, data display, light pen, printer, tablet, communicating receiver/transmitter, and are connected by appropriate adapters to the data and address busses 2 and 3. A read/ write or RAM 6 is attached to the data and address busses 2 and 3 and to a read/write (r/w) line 7 by means of which the microprocessor 1 can indicate whether or not it is reading from RAM 6 or writing into RAM 6.

(Image Omitted)

Not shown in Fig. 1 is the read-only store which would normally be used to store some of the control code for the microprocessor. Other control code, which may be downstream loaded via a communications link from a host computer (not shown) or loaded into the workstation on a magnetic diskette or other local storage medium (not shown) is stored in RAM 6 together with any data requiring processing by the microprocessor. As is well known, the various input/output devices indicate their need for service by the microprocessor by raising an interrupt signal on interrupt line 5. As is also well known, the microprocessor 1 performs a number of different tasks. These tasks may be independent of one another or may be interdependent in that one task requires the result of an earlier task. Some independent tasks might need to access the same storage location. each task requires several accesses by microprocessor 1 of RAM 6 either to read or write control code or data from or into RAM 6.

(Image Omitted)

For a correct operation of the workstation, it is essential that codes and/or data are not written into storage locations which are not allocated for use by the task currently being executed. Traditional main frame computers have had such a storage protection feature, but, as is explained above, the vast majority of microprocessors do not have a storage protection mechanism. Essentially this is because m...