Browse Prior Art Database

IBM Personal Computer-Based Automotive Electronic Diagnostic Character Set

IP.com Disclosure Number: IPCOM000062172D
Original Publication Date: 1986-Oct-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 3 page(s) / 109K

Publishing Venue

IBM

Related People

Kurtz, H: AUTHOR [+4]

Abstract

This article describes a method of modifying the character generator read-only memory (ROM) of the color graphics adapter in an IBM personal computer (PC) in order to implement special character symbols used in automotive applications. Once encoded into ROM these special symbols can be accessed in the alphanumeric mode similar to a standard ASCII character. Thus, a typical automotive repair manual page can be edited and displayed on the IBM PC-based automotive terminal using editor programs such as the IBM PC Personal Editor without the need to generate such a screen in the graphics all-points-addressable mode. This has the effect of greatly reducing the amount of storage and time required to generate such a screen.

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IBM Personal Computer-Based Automotive Electronic Diagnostic Character Set

This article describes a method of modifying the character generator read-only memory (ROM) of the color graphics adapter in an IBM personal computer (PC) in order to implement special character symbols used in automotive applications. Once encoded into ROM these special symbols can be accessed in the alphanumeric mode similar to a standard ASCII character. Thus, a typical automotive repair manual page can be edited and displayed on the IBM PC- based automotive terminal using editor programs such as the IBM PC Personal Editor without the need to generate such a screen in the graphics all-points- addressable mode. This has the effect of greatly reducing the amount of storage and time required to generate such a screen. Eight data bytes are required to specify such a symbol in all-points-addressable mode while one byte specifies it in the alphanumeric mode if the symbol is correctly encoded in ROM. The original character set stored in the character generator ROM of the color graphics adapter is shown in Fig. 1. The first 128 characters are standard ASCII characters. The remaining 128 characters are special characters which are useful in a variety of applications, such as foreign language alphabets, scientific and mathematical notations, block diagram generation, etc. Each character in this set is composed of an 8 x 8 cell, as shown in Fig. 2, which illustrates the bit pattern of character "A". The method disclosed herein modifies the last 128 characters of the ROM and implements the special character symbols used in automotive diagnostics applications shown in Fig. 3. Fig. 4 is a block diagram of the IBM PC Color Graphics Adapter used in the automotive terminal. The ROM is a Mostek MK36000-5 8K byte ROM with an access time of 300 ns and a cycle time of 450 ns. Its pin-out diagram is shown in Fig. 5A. The 356-character set takes up 2K bytes of memory, and it resides in the upper 2K of the ROM. The ROM address lines are configured...