Browse Prior Art Database

Character Generator

IP.com Disclosure Number: IPCOM000045032D
Original Publication Date: 1983-Jan-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 3 page(s) / 58K

Publishing Venue

IBM

Related People

Curlander, PJ: AUTHOR [+3]

Abstract

The above drawing shows a low-cost character generator which converts a coded information data stream and command data stream to a drop pattern of noncoded (NCI) data. The coded information (CI) and command information are passed to the character generator through a buffer shared with a master control processor. The NCI data is passed to an interlace logic (not shown) on a bus with an interlocked control protocol. The character generator includes a microprocessor 10. The microprocessor 10 communicates the status to the master control processor (not shown) through text buffers 0 and 1. The processor 10 builds a CI page in the CI buffer with data and commands from the text buffers. It also loads the font random access memory (RAM), sets CI and font pointers for normal printing, and performs diagnostics.

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Character Generator

The above drawing shows a low-cost character generator which converts a coded information data stream and command data stream to a drop pattern of noncoded (NCI) data. The coded information (CI) and command information are passed to the character generator through a buffer shared with a master control processor. The NCI data is passed to an interlace logic (not shown) on a bus with an interlocked control protocol. The character generator includes a microprocessor 10. The microprocessor 10 communicates the status to the master control processor (not shown) through text buffers 0 and 1. The processor 10 builds a CI page in the CI buffer with data and commands from the text buffers. It also loads the font random access memory (RAM), sets CI and font pointers for normal printing, and performs diagnostics.

The text buffers 0 and 1 form a communication link between the character generator and the master control processor (not shown). CI print data and formatting commands are passed to the character generator through these buffers. Status is passed to the master control processor from the character generator through these buffers.

The multiplexor controller 12 controls the character generator and the master control processor.

The CI buffer 26 is a 32K x 9 random-access memory. It holds one page of coded data. Each character is represented by three bytes. The first byte is an escapement byte which is composed of flags. The flags define the font to be used, if overlay is used, if a character is blank or a character is half indexed, and which direction. The second byte is a primary character byte which designates EBCDIC code for the character to be printed. In this byte, NUL (00) means print blanks until otherwise commanded. The overlay character designates the EBCDIC code for character to be overlaid and primary character, if overlay bit is set in escapement. The output of the CI buffer is the high-order address of the font buffer. This points the font buffer to the character box. At the beginning of each scan line, the microprocessor 10 sets a pointer in the external CI address register. This pointer is the address of the escapement byte of the first character in the scan line. This address is loaded into register 18 for initializing the high- order bits of a 1...