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Browse Prior Art Database

Addressing System for Display

IP.com Disclosure Number: IPCOM000083413D
Original Publication Date: 1975-May-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Curtis, KM: AUTHOR

Abstract

The drawing shows a system for displaying a character in a dot matrix that is formed in nine vertical slices. Each of these slices is stored as a byte in a store 2, and nine successive bytes are accessed to form the character. A keyboard 3 supplies a character code in seven bits. The 7-bit code corresponds to 128 characters, and store 2 holds nine bytes for each character. The fact that the number of slices, nine, is not an integral power of 2 complicates the storage accessing operation.

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Addressing System for Display

The drawing shows a system for displaying a character in a dot matrix that is formed in nine vertical slices. Each of these slices is stored as a byte in a store 2, and nine successive bytes are accessed to form the character. A keyboard 3 supplies a character code in seven bits. The 7-bit code corresponds to 128 characters, and store 2 holds nine bytes for each character. The fact that the number of slices, nine, is not an integral power of 2 complicates the storage accessing operation.

The first eight slices of a character are addressed conventionally. The seven- bit character code forms the low-order bits of a nine-bit address and two bits from counter 5 form the high-order bits. The counter is reset to begin a character forming operation and it is incremented as each slice of the character is formed. Each storage access supplies two bytes to a register 6, and the low-order bit of counter 5 selects the high byte and low byte in sequence for each storage access.

The two high-order bits of the address that are supplied by counter 5 divide store 2 into four parts. Thus, to display the first eight slices of the character A, store 2 is accessed successively at the following four addresses: 000000001

010000001

100000001

110000001.

The seven-bit code accommodates 256 characters. The actual character set of keyboard 3 is smaller, and some of the address locations in store 2 are unused in the addressing arrangement that has been described...