Terminal with viewports, auxiliary device attachment, and host-terminal flan control
First Claim
1. In a video display system including a displaycontroller responsive to row pointers specifying rows of display memory,viewport display defining means for defining how a given number of rows of display memory are to be displayed in a viewport having a number of display rows which is greater than the given number of rows of display memory, the viewport display defining means comprising:
- a null row of display memory which always contain codes indicating no display;
a table of row pointers corresponding to the viewport, the table having as many row pointers as there are display rows in the viewport and the row pointers including a row pointer to each of the rows in the given number of rows of display memory and a row pointer to the null row for each of the display rows which is not being used to display row of display memory; and
means for providing the row pointers in the table to the display controller,whereby the display controller correctly displays a viewpoint in which there is a greater number of display rows than there are display memory rows being displayed.
9 Assignments
0 Petitions
Accused Products
Abstract
In a dumb terminal to which an auxiliary device may be attached, improvements in display definitions. In the transfer of data between a host computer and the terminal or an auxiliary device, and in character generation memory. In the area of display definition, pages may be mapped onto the terminal'"'"'s display memory and viewports may be mapped onto pages. Page and viewport definition are independent of each other and settable modes permit a viewport to follow the active position. In the area of transfer of data, the source of data for the host computer and the destination of data from the host computer may be specified independently. Improvements in flow control ensure that the host computer can always change the destination of data and gain control of the terminal. Improvements in access control ensure that neither the terminal nor the auxiliary device can monopolize transfer between it and the host. Moreover, transfer can proceed transparently even when non-ASCII 8-bit codes or a 7-bit host-terminal link are involved. Finally, a protocol permits one portion of character generation memory to be copied to another portion thereof.
22 Citations
33 Claims
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1. In a video display system including a display
controller responsive to row pointers specifying rows of display memory, viewport display defining means for defining how a given number of rows of display memory are to be displayed in a viewport having a number of display rows which is greater than the given number of rows of display memory, the viewport display defining means comprising: -
a null row of display memory which always contain codes indicating no display; a table of row pointers corresponding to the viewport, the table having as many row pointers as there are display rows in the viewport and the row pointers including a row pointer to each of the rows in the given number of rows of display memory and a row pointer to the null row for each of the display rows which is not being used to display row of display memory; and means for providing the row pointers in the table to the display controller, whereby the display controller correctly displays a viewpoint in which there is a greater number of display rows than there are display memory rows being displayed.
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2. In display apparatus connected to a host processor and to an auxiliary device,
data transfer means for transferring data alternatively between the host processor and the display apparatus and between the host processor and the auxiliary device, the data transfer means comprising: -
first transfer means for transferring data from either the display apparatus or the auxiliary device to the host; second transfer means for transferring data from the host to either the display apparatus or the auxiliary device; and settable data transfer control means for controlling the first transfer means and the second transfer means independently of each other, the settable data transfer control means being settable to cause the first transfer means to transfer data received from either the display apparatus or the auxiliary device and to cause the second transfer means to provide data to either the display apparatus or the auxiliary device. - View Dependent Claims (3)
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4. In display apparatus having both a display memory divisible into display positions and an output device for outputting a display divisable into display lines,
means for defining the display comprising: -
means for defining a page, the page including a specified set of the display positions; means for defining a viewport on the output device, the viewport including a specified set of the display lines; correspondence establishing means for establishing a correspondence between a member of the set of display positions and a member of the set of display lines; and means for outputting on each display line the contents of any corresponding display positions and when the correspondence establishing means has established no correspondence between any member of the set of display positions and a given member of the set of display lines, outputting certain display data on the given display line, whereby no correspondence is required between a set of display positions and a member of the set of display lines, permitting the page and the viewport to be defined independently of each other. - View Dependent Claims (5, 6, 7, 8, 9, 10, 11)
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12. In display apparatus having a display memory divisible into at least one set of display positions and an output device for outputting a display divisible into at least one viewport and means for establishing a correspondence between a given set of display positions and a given viewport such that the given viewport displays at least a portion of the given set of display positions,
means for defining the display comprising: -
specification means for specifying an active display position in the display positions and an active viewport displaying a first portion of the set of display positions to which the active viewport corresponds, the first portion including the active display position and in the means for establishing a correspondence, auto alignment means for responding to the specification means by establishing a new correspondence between the active viewport and a second portion of the corresponding set of display positions including the active position when the specification means specifies that the active display position is no longer in the first portion. - View Dependent Claims (13, 14)
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15. In display apparatus having a display memory divisible into display positions, each display position belonging to one page of a plurality of pages in the display memory, and an output device for outputting a display divisible into at least one viewport of a plurality of viewports, the viewport being assignable to one of the pages and displaying a set of display positions on the page to which the viewport is assigned, and means for establishing a correspondence between a given viewport and a given page to which the given viewport is assigned and between the given viewport and a given set of display positions on the given page such that the given viewport displays at least a portion of the given set of display positions,
means for defining the display comprising: -
specification means for specifying an active display position in the display positions and an active viewport of the viewports; and in the means for establishing correspondence, auto mapping means for responding to the specification means when the specification means specifies that the active display position is presently in another page by assigning the active viewport to the other page. - View Dependent Claims (16, 17, 18, 19)
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20. In display apparatus controllable by protocols, having a display memory divided into display positions, and having means for defining rows and pages in the display memory such that each display position belongs to a row and a page,
means for copying a first set of the display positions into a second set of the display positions comprising: -
a copy region protocol which specifies the first set of display positions by specifying a first page, a starting row, and a number of rows on the first page and specifies the second set of display positions by specifying a second page and a starting row on the second page and means in the display apparatus responsive to the copy region protocol for copying the contents of the first set of display positions into the second set of display positions. - View Dependent Claims (21)
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22. In display apparatus which is responsive to protocols and which includes display output means and character generation means including writable character generation memory means containing visual representation data from which the display output means generates a visual representation of a character, means for copying visual representation data from a first portion of the character generation memory means to a second portion thereof comprising:
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a copy character generation memory protocol specifying the location of the first portion and of the second portion; and means responsive to the copy character generation memory protocol for copying the visual representation data contained in the first portion into the second portion. - View Dependent Claims (23, 24)
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25. In display apparatus which is connected to a host processor and to an auxiliary device, responds to destination protocols from the host processor specifying either the display apparatus or the auxiliary device as a destination for data from the host processor, and provides at least a termination protocol requesting termination of transmission to the host processor, a method performed by the display apparatus to ensure that the display apparatus can respond to one of the destination protocols comprising the steps of:
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monitoring a receiving buffer for receiving protocols from the host processor to determine whether the buffer can accomodate the destination protocol; sending the termination protocol to the host processor while the buffer can still accomodate the destination protocol; continuing to receive protocols in the receiving buffer; and continuing to process the protocols in the receiving buffer, whereby the display apparatus is always able to receive and process a destination protocol sent by the host processor in response to the termination protocol. - View Dependent Claims (26)
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27. In display apparatus which is connected to a host processor and to at least one other data source and which provides data from itself and the other data source to the host processor,
a method performed by the display apparatus for ensuring that the host processor is provided data from all of the sources including the display apparatus comprising the steps of: -
providing a next tag identifying a next source of data to the processor; providing data from the next source to the processor for a limited period; and repeating the above steps so that each of the sources is a next source.
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28. In display apparatus which is connected to a host processor and to another data source and provides protocols from itself or from the other data source to the host processor,
a method performed by the display apparatus for informing the host processor that the source not currently providing data has data comprising: -
determining that the source not currently providing data has data to provide; and inserting a message waiting protocol among the protocols currently being provided to the host processor.
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29. In display apparatus which is asynchronously connected to a host processor, which provides protocols to the host processor, and which responds to protocols received from the host processor by placing the received protocols in a receive buffer and interpreting the received protocols after they have been placed in the receive buffer,
a method of guaranteeing that the display apparatus will respond to the host processor comprising the steps of: -
sending a reset protocol from the host processor to the display apparatus; responding in the display apparatus to the reset protocol by not placing the reset protocol in the receive buffer and immediately performing steps including clearing the receive buffer; cancelling processing of any protocol which the display apparatus is interpreting at the time the display apparatus receives the reset protocol; and enabling the receive buffer to again receive protocols. - View Dependent Claims (30)
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31. In display apparatus connected to a host computer and to an auxiliary device and wherein the display apparatus provides 8-bit ANSI (American National Standards Institute) protocols to the auxiliary device and receives 8-bit ANSI protocols therefrom but the host computer produces and responds to other protocols for control of the auxiliary device which are not 8-bit ANSI protocols,
a method performed by the display apparatus for operating transparently when the host computer employs the other protocols to control the auxiliary device comprising the steps of: -
while the display apparatus is receiving the other protocols from the host computer for transfer to the auxiliary device, converting the other protocols into the equivalent ANSI 8-bit protocols and providing the equivalent ANSI 8-bit protocols to the auxiliary device; and while the device apparatus is receiving ANSI 8-bit protocols from the auxiliary device for transfer to the host computer, converting the ANSI 8-bit protocols into the equivalent other protocols and providing the equivalent other protocols to the host processor. - View Dependent Claims (32)
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33. The method set forth in claim 36 and wherein:
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the display apparatus has a first mode of operation wherein the display apparatus transfers protocols unchanged between the host processor and the auxiliary device and a second mode of operation wherein the method of claim 36 is performed upon protocols transferred between the host processor and the auxiliary device and the performance of the steps of the method of claim 36 is preceded by a step wherein the display apparatus receives a protocol from the host processor which specifies the second mode of operation and responds thereto by enabling the second mode of operation.
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Specification