Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
158 words
A raster scan video display terminal comprising memory means for storing a plurality of rows of characters to be displayed, a buffer for storing one row of characters during the line scans in which it is displayed, a dot matrix character generator responsive to the buffer contents and line counter means to provide a video signal for display of the characters, and means for transferring characters row by row from the memory means to the buffer during each frame of the raster scan, characterised in that memory means also store in respect of each row corresponding description information comprising the address of the first character to be displayed in that row and a pointer address for the description information for the next row to be displayed, and in that the means for transferring respond in respect of each row to the first character address in the description information pointed to by the description information for the preceding row.
Claim 2
Dependent Claim
158 words
A raster scan video display terminal comprising memory means for storing a plurality of rows of characters to be displayed, a buffer for storing one row of characters during the line scans in which it is displayed, a dot matrix character generator responsive to the buffer contents and line counter means to provide a video signal for display of the characters, and means for transferring characters row by row from the memory means to the buffer during each frame of the raster scan, characterised in that memory means also store in respect of each row corresponding description information comprising the address of the first character to be displayed in that row and a pointer address for the description information for the next row to be displayed, and in that the means for transferring respond in respect of each row to the first character address in the description information pointed to by the description information for the preceding row.
Claim 3
Dependent Claim
22 words
A terminal according to claim" 1, characterised in that the memory means is updated during the vertical retrace intervals of the scan.
Claim 4
Dependent Claim
14 words
A terminal according to claim 2, characterised-in that only rows which change are updated.
Claim 5
Dependent Claim
19 words
A terminal according to claim 2 or 3, characterised in'that the description information is only updated when it changes.
Claim 6
Dependent Claim
28 words
A terminal according to any of claims 1 to 4, characterised in that attribute information is also stored in the memory means in association with each stored character.
Claim 7
Dependent Claim
30 words
A terminal according to any of claims 1 to 5, characterised in that the row description information also includes an indication of the number of characters in a complete row.
Claim 8
Dependent Claim
47 words
A terminal according to any of claims 1 to 6, characterised in that the row description information also includes an indication of the first raster line of the character row to be displayed and of the number of raster lines of the character row to be displayed.
Claim 9
Dependent Claim
35 words
A terminal according to any of claims 1 to 7, characterised in that the row description information also includes an indication of the end of the frame, vertical synchronization and blanking during the vertical retrace.
Claim 10
Dependent Claim
60 words
A terminal according to any of claims 1 to 8, characterised by register means for storing the row description information pertaining to the current row, and in that the row description information pointed to by the contents of the register means is transferred to the register means in the horizontal retrace interval following the last line scan of each row.
Claim 11
Independent Claim
53 words
A method of operating a terminal according to any of claims 1 to 9, characterised in that characters are stored in strings larger than can be displayed in a row and in that horizontal scrolling is effected without changing the stored strings by altering the first character address in the row description informations.
Claim 12
Dependent Claim
49 words
A method of operating a terminal according to claim 7, characterised in that smooth vertical scrolling is effected by progressively incrementing the number of the first line to be displayed and correspondingly decrementing the number of raster lines to be displayed, during the course of a plurality of frames.