Browse Prior Art Database

Adapter Card for Host-Printer Interfaces

IP.com Disclosure Number: IPCOM000035050D
Original Publication Date: 1989-May-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 57K

Publishing Venue

IBM

Related People

Cocuzza, CD: AUTHOR [+2]

Abstract

A single, more efficient adapter circuit card can be used between the interfaces of a host processor system and attached printer by allowing the direct memory access (DMA)controllers of both the host and printer to write into or read from random-access memory on the adapter and downloading microcode from the printer to the adapter each time the printer is powered. Referring to the schematic of the adapter card in the figure, the card is connected to the host interface through Link-TC module 1 and to the printer interface, identified as Task, via data and address buses 2, 3 and 4, and initial microcode (IML) and Task control lines 5, through respective registers 6. The host uses a serial, bidirectional, asynchronous communication system and initiates all communications.

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Adapter Card for Host-Printer Interfaces

A single, more efficient adapter circuit card can be used between the interfaces of a host processor system and attached printer by allowing the direct memory access (DMA)controllers of both the host and printer to write into or read from random-access memory on the adapter and downloading microcode from the printer to the adapter each time the printer is powered. Referring to the schematic of the adapter card in the figure, the card is connected to the host interface through Link-TC module 1 and to the printer interface, identified as Task, via data and address buses 2, 3 and 4, and initial microcode (IML) and Task control lines 5, through respective registers 6. The host uses a serial, bidirectional, asynchronous communication system and initiates all communications. Sixteen bit frames are used and include a sync bit, printer address, parity bit and data or command byte that are decoded by the adapter. Print data are reformatted and written across the Task interface into the printer RAM shared with the printer engine. The adapter card carries microprocessor 7 and shares data and address buses with Link-TC module 1 and RAM 8. The bus structure allows the DMA controller of module 1 to directly write into or read from the memory of microprocessor 7 without buffers or arbitration logic. DMA cycles are performed using the HOLD and HOLDA signals of the microprocessor. No bus switching is required since the upper and lower data buses are tied together. Task interface timings are generated by discrete logic gates and flip-flops. On printer power-up, microcode is downloaded from the printer diskette...