The present invention relates to digital microprocessing facilities for use in printers, enabling the printer to generate cursive writing, with particular emphasis on output devices for data processing facilities, and with further emphasis on utilization of the facility in conjunction with matrix printers, having print elements such as needles, styli, hammers or the like, arranged in one or several columns.
Printing facilities of the type to which the invention pertains generally include a symbol or character generator, a processing facility that calls on the symbol generator in a sequence for purposes of readout of digital representation of particular characters and symbols, and a driver circuit for driving the various print elements in accordance with a program that uses the character representing bits to generate the respective character or symbol. Each of the character is composed on a dot column by dot column basis under utilization of one or a plurality of the individual print elements as they are arranged in a column. They are actuated sequentially as the print process moves from column to column.
The columnar arrangement of the print elements on one hand, and the concurrency of print elements actuation entail a generally vertical oriented appearance of each character. However, if one interposes (e.g. by means of variable length shift registers) delays for triggering of the several print elements, one can generate an oblique character appearance--a cursive writing style.
Data output devices generally and matrix printers in particular are usually required to process a large amount of data furnished to them by a computer. This processing must occur in a relative short period of time whereby it has to be borne in mind that from the point of view of computer operation the physical print process, no matter how fast it appears to be, is a relatively slow process, and a high speed operation is desired in order to avoid unnecessary pauses in computer operation.
Generally speaking, the processing of raw data may involve the processing of information which permits display, for example, on a monitor screen in a terminal or printout of such data in order to obtain a permanent record, whereby the latter is, of course, a relatively slow process. The matrix printers that are used in many instances pose in addition certain problems of slowness, simply on account of composing characters individually out of a multiple of dots. On the other hand, economic considerations have led to a widespread adoption of matrix print technology.
A computer generally, will transmit binary signals from its working memory or a memory extension, including relatively slow external data storage facilities, to an output device generally and in particular to a matrix printer. Herein then lines and columns of a character matrix to be printed are determined as stated by the function, operation, and design of the symbol or character generator. The binary signals, moreover, will also control a certain enhancement of printing, for example, in case of high quality print operation, and this increase is either produced in the data station or directly on the print medium.
An interpositioning of digital micro-processors between the computer generating the data to be printed out generally and the print process proper is generally known in order to obtain certain autonomy on part of the print facilities, so that the printer does not tie up to the computer operation directly.
After this general background, reference is made to German printed patent application No. 24 57 884, which is a representative example of a buffering type digital microprocessor. The reference particularly refers to the utilization of a micro-processor for purposes of generating cursive writing. As stated, cursive writing basically requires a transposition of the printing process such that originally envisioned (as far as the character generator is concerned) vertical lines are converted into lines of oblique orientation. Generally speaking, this requires a controlled delay in the printing process as carried out by dot printing elements and on an element for element basis as far as the vertical column of print elements is concerned.
Under normal circumstances (vertical line printing), elements participating in the printing of a vertical line are triggered and operated simultaneously. For purposes of cursive writing these elements have to be actuated in sequence with a non-zero time interval being interposed in between the actuation of two vertically juxtaposed print elements. One has to provide, therefore, individual delay devices to be effective between the character generator on one hand and the driver circuit for the electromagnetic operation of the print element on the other hand. These delay devices, shift registers and logic circuitry permit the selective operation of cursive or normal writing.
The known micro-processor, however, does not satisfy requirements for fast control and at speed sufficient to meet speed requirements as they are necessary in some processing stations in matrix printers. The known method of cursive writing does not consider the fact that matrix printers and other printout and readout stations operate bidirectionally for reasons of avoiding seemingly unnecessary return trips of equipment, towards a given starting position. In other words, the known solution of obtaining cursive writing will be able to work only for printing oblique symbols, when the print process runs, for example, from left to right. In the case of any subsequent printing from right to left these known devices simply are not capable of consistently presenting a cursive letter image. Consequently, the known cursive writers are tied to a significant speed cut. Another disadvantage of the known method is a fixed angle of obliqueness.