🚀 go-pugleaf

One good source of public-domain programs is Antic magazine.  They have some
public-domain and low-cost programs that I'm certain to get (sorry, it's at
home so I can't give examples).  Anyone who wants to do serious things with an
ST should subscribe to Antic and probably Analog as well.

It was from one of these magazines (Antic, I think) that I learned that the 520
ST has the ability to interrupt at the start of the horizontal and vertical
retrace intervals.  In those intervals you can change things like the color
registers (which is what the example program did) and also, I hope, the
starting address for the bitmap.  If you can change the bitmap's address on
every vertical retrace you can do really nice smooth scrolling.  If you can
change it on every horizontal retrace as well you could provide (full-width
only) windows very efficiently.

Unfortunately, if the ST documentation tells you how to do this kind of thing I
haven't found it yet.  I was rather annoyed that the hardware descriptions that
came with the developer's kit told me about the keyboard, the sound chip, the
DMA chip, and the diskette driver chip, but not a word about the display chip.
Have later developer's kits remedied this problem?  Or is the information
buried somewhere I haven't found yet?

	Dan Franklin        dan@bbn-prophet.arpa    ima!bbncca!dan