| 摘要 |
A raster scan cathode ray tube (CRT) display system which is capable of indirectly addressing data to be displayed in an manner presenting the data on any selected row or group of rows, in any order. A scrolling system according to the invention includes a cathode ray tube controller (CRTC) coupled to an indirect address counter which is coupled together with a presettable counter through a multiplexer (MUX) to the address port of a CRT display refresh memory (RAM), a segment of the data output port of the refresh memory being coupled to the preset port of the presettable counter. The invention operates by generating a refresh address indirectly through the presettable counter which addresses pointers in the refresh memory, each pointer containing the absolute address of the beginning of a specific line of data in the refresh memory which is to be displayed. During the blanking interval of the display, data is addressed by the indirect address counter. During other intervals, the address presented to the refresh memory is generated by the refresh address counter (the presettable binary counter). The address which is provided at the refresh address counter dictates the line of characters which are therafter displayed.
|
