Browse Prior Art Database

Printer Head Control Command Look-Ahead and Overlap

IP.com Disclosure Number: IPCOM000061107D
Original Publication Date: 1986-Jun-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 3 page(s) / 53K

Publishing Venue

IBM

Related People

Cavill, BR: AUTHOR

Abstract

A technique is described whereby an algorithm used in conjunction with a print mechanism control microprocessor (PMCM) and a head control microprocessor (HCM) provide an overlap of print head movement commands and a look-ahead feature. Early notification of print head movement, through the use of an anticipation algorithm, permits directional and speed changes of the print head to take place while the head is operating under a previous instruction. This look-ahead and overlap command function provides for faster printer throughput and provides smooth operation, since repeated stopping of the print head to await instructions is eliminated. In prior art, print head mechanisms were required to complete their individual instruction and come to a stop before proceeding with the next instruction.

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Printer Head Control Command Look-Ahead and Overlap

A technique is described whereby an algorithm used in conjunction with a print mechanism control microprocessor (PMCM) and a head control microprocessor (HCM) provide an overlap of print head movement commands and a look-ahead feature. Early notification of print head movement, through the use of an anticipation algorithm, permits directional and speed changes of the print head to take place while the head is operating under a previous instruction. This look- ahead and overlap command function provides for faster printer throughput and provides smooth operation, since repeated stopping of the print head to await instructions is eliminated. In prior art, print head mechanisms were required to complete their individual instruction and come to a stop before proceeding with the next instruction. The concept described herein utilizes a PMCM to issue commands to an HCM which decodes the commands so as to control the head carriage motor. The HCM determines the location where stopping must be initiated, calls the stop target, and calculates a projected stop location target. The HCM also calculates the head speed to be traveled, based on the maximum allowable speed for a particular wire fire density. The information is then saved in temporary registers since another print or move command may still be in the progress while the present command reception and decode is taking place. When a ready command is initiated, the HCM moves the information to motion registers and the command ready bit is set off. After loading the run registers, another positional target is calculated, which is the target the head will reach ten milliseconds before stopping. This is called the early warning target and indicates when the PMCM will be notified that the command is completed. By notifying the PMCM that the command is completed early, the PMCM can then set up and issue the next command before the stopping of the head. At zero velocity, the command is initiated and motion continues without interruption. When the PMCM is notified of a command completion, a new motion command can be processed by the HCM. In order for the PMCM to set up commands, using an algorithm to decide the most efficient way to move the head, it must be told where the head will be when the current command is completed. The HCM is able to predict and feed back the prediction to the PMCM in anticipation of where the head will be at the end of a particular motion. This instructional overlap is made when a command is decoded and is part of the information saved. An example of the different types of motions the algorithm is capable of handling is shown in Fig. 1, where the velocity of the head movement is plotted against the distance traveled. In general, it is possible to go from 3.0 to 40 inches/second to any other speed in the same direction without stopping. The advanced command look-ahead and overlap from early notification of command com...