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SD SYSTEMS - VDB 8024 Video Display Board
This was one of SD Systems most successful products. This video board gave a rock solid 24 line X 80 characters per line B/W display. Its onboard Z80 made screen update instantaneous. It takes a parallel ASCII type keyboard for input.

SD Systems VDB 8024

The VDB utilizes a Z80 microprocessor to perform the control functions of a video terminal.  These functions include LF, CR, full cursor control, home, clear, scroll and back space.  In addition to the basic function several special additional features are provided.  One of these features provides for specified fields of characters to be enhanced.  This field can be enhanced in any of the following ways: Underline, Reverse, Blink, Protect or combinations.  Another feature of this board is the programmable character generator-  This is a 7 x 8 dot character matrix with 2 bits of descenders to provide upper and lower case characters in a 7 x 10 dot field.  128 characters are typically available while 256 characters can be made available using a 2K x 8 PROM.  These characters are displayed in a field of 80 characters in length and 24 lines per page.  The VDB processor runs only during H & V sync to eliminate any disturbance of the display due to the processor running during the raster scan.  There are several software controllable functions.  These include a speed control similar to a baud rate control and also a scroll up or scroll down.  In addition, a set of 32 special characters are available.
The VDB hardware performs all control and timing functions as well as the special enhancement functions.
The on board CRT 5027 video timer and controller is used to perform character count, character line count and row count.  The outputs of these counters are then fed into the RAM or Character Generator (CGEN) to provide the proper scanning and display of each character in its proper place.  This chip also provides for proper cursor control, horizontal sync, vertical sync and blinking signals.
The Z80 executes the software which controls all functions of the system.  This includes inputting data, storing data in memory, initializing the CRT 5027, controlling the special functions, cursor control and scrolling. 
The manual can be obtained here


Other SD Systems  S-100 Boards
8024 VDB    ExpandoRAM    ExpandoROM     SBC    VersaFloppy I & II   Z8800   PROM-100  
I/O8 Serial Board  4KRAM   Other Boards


This page was last modified on 01/08/2011