Video Generation
Galaksija did not have a dedicated video circuitry. Inspired by the CDP 1802 application book, its Z80A CPU was directly responsible for modulating the monochrome video signal with a little help of a shift register. Galaksija's CPU would write one byte to the shift register, which would, in turn, serialize its 8 bits one by one to the video output.
Since Galaksija had little RAM, a portion of it was taken not to store information for each pixel separately but character codes. CPU then had to look up character definitions in its character definitions ROM to find the values to send to the shift register.
This was standard operation available in Galaksija's ROM. Some software, however, reportedly took the responsibility for driving the shift register (and thus generating video) and was able to use various tricks to achieve what appears as high-resolution graphics, such as with user defined graphic characters.
It was thus possible for Galaksija with sufficient RAM upgrade (having at least 6144 bytes available for video memory) to achieve 256x208 graphics without any specialized circuitry. Other resolutions were also possible while maintaining only pixel width, by changing the amount of the active area of video picture and/or handling two interlaced video fields separately. Changing the number of active lines would have also altered the CPU usage for video generation and ratio of it available for other use.
Read more about this topic: Galaksija (computer)
Famous quotes containing the words video and/or generation:
“These people figured video was the Lord’s preferred means of communicating, the screen itself a kind of perpetually burning bush. “He’s in the de-tails,” Sublett had said once. “You gotta watch for Him close.””
—William Gibson (b. 1948)
“And his master commended the dishonest manager because he had acted shrewdly; for the children of this age are more shrewd in dealing with their own generation than are the children of light.”
—Bible: New Testament, Luke 16:8.