Screen Saver/Restorer

By Robert Sprowson

Originally published in EUG #48

This file describes the program SSAVER, an event-driven screen saver for the 8-bit Acorns using a 6845 cathode ray tube controller.


At the > prompt, type *RUN SSAVER.

The program will then load. It will not be configured so will appear not to have done anything at all.

You can then configure the screensaver to restore the screen on the occurence of any event (See your User Guide under *FX 14 or *FX 13 for details of event no.s).

Now, at the new > prompt, type CHAIN"SSTEST" (RETURN).

This will run a really simple program that demonstrates the use of a new OSWord call that sets up the saver to your requirements.

The format of the OSword has been defined as follows:

      Entry A=&E0
         X and Y point to a 10 byte parameter block in memory
         XY+00=Two byte delay in 50ths of a second
         XY+02=1st event number to unblank the screen
         XY+09=8th event number that will unblank the screen
      Exit  Parameter block unchanged
The tester program sets event 2 (Key pressed event) to restore the screen, but you may wish to set it to respond to a different event. Note that if you don't want eight different events to restore the screen, simply pad the other values with a duplicate of one you've already used. (This is because I couldn't use a padding value since event numbers cab be any value in the range 0-255!)

You may reconfigure the screen saver as many times as you want without having to run it again. Simply call the OSWord.

Exit Messages


Known Problems/Future Enhancements

No known problems.


v0.90Original development version
v1.00Released to EUG, having fixed a problem with frame sync on proper computer monitors (It was previously only tried on a domestic TV).

Manual (C) 1999 Robert Sprowson
Software (C) 1999 SPROW