Browse Prior Art Database

Mapping Box

IP.com Disclosure Number: IPCOM000036463D
Original Publication Date: 1989-Oct-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 3 page(s) / 98K

Publishing Venue

IBM

Related People

Hailpern, BT: AUTHOR [+3]

Abstract

A mapping box is a device that serves as an interface between a processor (or microprocessor) and its storage. Some storage will be local and some will be remote. The processor is referred to as a terminal processor because it is expected that the mapping box will be used to extend the memory of intelligent terminals.

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Mapping Box

A mapping box is a device that serves as an interface between a processor (or microprocessor) and its storage. Some storage will be local and some will be remote. The processor is referred to as a terminal processor because it is expected that the mapping box will be used to extend the memory of intelligent terminals.

The mapping box device consists of a controlling microprocessor, four control registers and memory for a mapping table, as shown in Fig. l. Three of the control registers specify capabilities as described below, corresponding to the current instruction, data source, and data sink address spaces. The fourth register holds mapping box status and control information. The mapping table is used to implement the capabilities. The box has two sets of input/output lines, each containing data and control lines. The I/O lines connect to the terminal processor and to a bus leading to the remote memory. Logically, the four control registers are part of the address space of the terminal processor, i.e., they set and retrieve under software control.

The terminal processor presents the mapping box with data and addressess. Addresses below certain value reference local memory and above that value refernece remote memory. Remote addresses may be logically defined as a pair (r,a), where r represents one of the three control registers and a is the address within the address space pointed to by register r. Physical realization would most likely be as a single, extended address. The mapping box passes the pair consisting of the contents r and a on the control line to the remote memory bus along with any data on the data line in the case of write operations.

The terminal processor may change the contents of the control registers in order to access different address spaces. Such changes would only be allowed by the controlling microprocessor if the new capabilities are compatible with its mapping table. Changes to the mapping table would be allowed only by a central processor that manages the remote memory.

The mapping box device allows independent access to instruction stream, data source stream and data sink stream through the three control registers. The actions of the box are independent of the terminal processor's instruction set, allowing many different kinds of processors to use the remote memory. It is independent because all that is presented to the mapping box device is an address (and sometim...