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Pipelined Data Transfer for Grey-Scale Electrochromic Display

IP.com Disclosure Number: IPCOM000041415D
Original Publication Date: 1984-Jan-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 3 page(s) / 27K

Publishing Venue

IBM

Related People

Bird, CL: AUTHOR [+5]

Abstract

Images are written on an array of electrochromic display picture elements (pels) by supplying an electric charge of a predetermined magnitude to selected pels over the array. The display technology is such that the intensity of coloring of a pel is proportional to the length of time for which the charging current is applied. When displaying a grey-scale image, it is convenient to build up the image by a series of binary weighted write operations to the array, doubling or halving the write time between one operation and the next. Thus for example, by judicious application of three different write times of 1/7T, 2/7T, and 4/7T to the pels in the array (where T is the write time for maximum intensity), images containing eight gradations of grey scale are progressively built-up.

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Pipelined Data Transfer for Grey-Scale Electrochromic Display

Images are written on an array of electrochromic display picture elements (pels) by supplying an electric charge of a predetermined magnitude to selected pels over the array. The display technology is such that the intensity of coloring of a pel is proportional to the length of time for which the charging current is applied. When displaying a grey-scale image, it is convenient to build up the image by a series of binary weighted write operations to the array, doubling or halving the write time between one operation and the next. Thus for example, by judicious application of three different write times of 1/7T, 2/7T, and 4/7T to the pels in the array (where T is the write time for maximum intensity), images containing eight gradations of grey scale are progressively built-up. Generally the production of a grey-scale image is under control of a computer supplying a series of records to a display adapter. Each record contains information identifying a row number of the pel array to be written: a binary intensity code (two bits in the case of eight grey-scale levels) specifying the duration of the selected writing period, and a pattern of '1' and '0' bits by means of which the pels in the associated row to be written are identified. In order to display a complete grey-scale image, records in respect of each pel row and each intensity code are transferred in turn to a gating register within the display adapter from where they are used to gate the appropriate patterns of charge to the selected rows of the electrochromic array. Since the time required to transfer a record from the controlling computer to the display adapter is the same for all write times, the overall time taken to generate a complete image is minimized by overlapping the data transfer time for a record with the actual analog write operation for the previous record. To do this, the adapter is provided with sufficient random-access storage to hold up to three pel rows/intensity records as a queue. Then, following each analog write operation, the adapter selects the next record from the queue and loads its bit content into the gating register ready to control the next analog write operation. During each write operation, the adapter accepts a new record from the controlling computer only if the queue is empty, or if not full, the remaining write time of the current write operation exceeds that of the shortest duration write operation. By this means, data transfer is encouraged to occur during the longer analog write periods and discouraged during the shorter write periods. The resulting pipeline appearance of the data transfer is illustrated by the two waveforms in the figure on the next page. A repetitive sequence of analog write time periods of duration
0.275 msec (1/7T), 0.55 m...