What about adding graphics facilities to an existing nongraphics computer system? Fig. 2-30 illustrates a device that can be retro-fitted into the popular ADM-3A serial terminal to allow full-blown high-resolution plotting and graphing. The device is a pc board that fits inside the ADM-3A case under the regular ADM board. It contains a Z-80A microprocessor, with 512 by 250 plotting resolution and a Tektronix software compatibility option. The product is made by Digital Engineering, Inc., in California and is called the RG-512.
Fig. 2-28. Block diagram of an image digitizer for S-100 based computers.
Fig. 2-29. Examples of digitized output from the CAT-100.
Fig. 2-31 shows a block diagram of the RG-512. A special attraction of the device is that it features a vector mode for plotting lines from user-specified end points, a selective erase function so specific vectors can be removed, a point mode, and an annotation mode for mixing in text from the ADM terminal. As you can see in the block diagram, the RG-512 simply mixes its output in with the normal ADM text output so both are passed to the screen.
The actual plotting resolution is just short of amazing and it means very exciting graphics potential for nongraphics computer systems.
Fig. 2-30. Retro-Graphics RG-512 unit fits inside standard ADM-3A terminal (shown) and allows point plotting and vector graphics on a 512 × 250 matrix.
Fig. 2-31. Block diagram of Retro-Graphics 512 × 250 video graphics add-on.
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