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Attachment of Electrochromic Display to Personal Computer

IP.com Disclosure Number: IPCOM000062293D
Original Publication Date: 1986-Nov-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 13K

Publishing Venue

IBM

Related People

Halliwell, H: AUTHOR

Abstract

An electrochromic display is attached to a personal computer (PC) via a simple adapter card to emulate the PC display. Because of the relative slowness of an electrochromic display in comparison with a CRT, the arrangement uses PC resident software to display only stable full screens of data when the PC display buffer has not changed for some time and the PC processor is idle. Thus, the electrochromic display will follow the PC display but not instantaneously. This arrangement uses co-resident software based on three standard PC interrupts: two hardware and one software. These are installed by the standard method of replacing the address stored in the interrupt vector. In each case the existing address is preserved so that the standard action for those interrupts can be taken in addition to the actions described here.

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Attachment of Electrochromic Display to Personal Computer

An electrochromic display is attached to a personal computer (PC) via a simple adapter card to emulate the PC display. Because of the relative slowness of an electrochromic display in comparison with a CRT, the arrangement uses PC resident software to display only stable full screens of data when the PC display buffer has not changed for some time and the PC processor is idle. Thus, the electrochromic display will follow the PC display but not instantaneously. This arrangement uses co-resident software based on three standard PC interrupts: two hardware and one software. These are installed by the standard method of replacing the address stored in the interrupt vector. In each case the existing address is preserved so that the standard action for those interrupts can be taken in addition to the actions described here. For the purposes of explaining the algorithm, 80-column, 25-row text emulation is taken as an example. It can be applied to the other display modes by changing the parameters. The three interrupts can be viewed as parallel processes for the sake of this description. Timer Interrupt This is a hardware interrupt that occurs about 18.2 times per second. The action of the added function is to poll the electrochromic display and to look for differences between the PC display buffer and a copy of it maintained by this algorithm, as follows: During the timer interrupts: 1a.One row of the PC display buffer is compared with its copy. If there has been a change, the copy is made equal to the row in the display buffer. This will be done once for each of the 25 rows in a cycle of 27 timer interrupts. 1b.A poll is issued to the electrochromic display. This will be done twice in a cycle of 27 timer interrupts.
2.The standard action for the timer interrupt is taken, i.e., to update the time-of- day clock and to invoke a software interrupt that applications can use. The full cycle of 27 timer interrupts takes about...