griffith@eecs.cs.pdx.edu (Michael Griffith) (09/15/90)
aiajms@castle.ed.ac.uk (-=Andy=-) writes: >Could someone explain the above copper registers. I know that they are >for screen addressing but the book I have which explains how they work >is not very clear. [ddfstrt ddfstop diwstrt diwstop] I am posting this followup to comp.sys.amiga.tech because that is where the answer belongs, but I am cross-posting it to comp.sys.amiga because that is where the article originated. DIWSTRT & DIWSTOP (Display Window Start & Stop): These registers control the position of the display window on the screen. They define the physical area that the display screen will occupy. DDFSTRT & DDFSTOP (Display Data Fetch Start & Stop): These registers control when the DMA fetching of the display data is performed. It tells the machine how long on a vertical trace to wait before starting to fetch the data, and how long until the data is to stop being fetched. DIWSTRT and DIWSTOP are normally used to control the positioning and size of the display area on the screen. DDFSTRT and DDFSTOP ensure that the data is fetched correctly for the display area. You also need to alter these to fetch an additional word for scrolling sometimes, etc. Hope this explains some of what you wanted to know. | Michael Griffith | If I had an opinion it certainly | | griffith@eecs.ee.pdx.edu | wouldn't be the same one as | | ...!tektronix!psueea!eecs!griffith | Portland State University anyways. |