MANUAL FOR SSAVER (6502 machine code)

This file describes the program SSAVER which is an event driven screen saver
for the 8 bit BBC micros using a 6845 cathode ray tube controller.
The manual and software is (C)1997 SPROW

INSTRUCTIONS-
At the command prompt,type *RUN SSAVER

The program will then appear to not have done anything.This is because the 
screen saver has simply been loaded,and not configured yet!
You can configure the screensaver to restore the screen on the occurrence of
any event (see your User guide under *FX14 or *FX13 for details of event nos).

Next,at the BASIC prompt,type CHAIN"SSTEST"

This will run a really simple program that demonstrates the use of a new OSWord
call which sets up the screen saver to your requirements,in this particular
case it sets a delay of about 10 seconds restoring the screen with a keypress.

The technical details of the OSWord have been defined as follows:
Entry A=&E0
      X and Y point to a 12 byte parameter block in memory
      XY+00=10
      XY+01=0
      XY+02=Two byte delay in 50ths of a second
      XY+04=1st event number to unblank the screen
        :
      XY+0B=8th event number that will unblank the screen
Exit  Parameter block unchanged

A delay of 0 at XY+02 effectively turns off the screensaver.

Note that if you don't want 8 different events to restore the screen simply
pad the other values with a duplicate of one you've already used,eg.
      XY+00=10
      XY+01=0
      XY+02=5000 (about 100 seconds)
      XY+04=2 (screen comes back when a key is pressed)
      XY+05=7 (screen comes back when a serial port error occurs)
      XY+05=7 (padding)
      XY+05=7 (padding)
      XY+05=7 (padding)
      XY+05=7 (padding)
      XY+05=7 (padding)
      XY+05=7 (padding)

You may reconfigure the screen saver AS MANY TIMES as you want without having
to run the "SSAVER" programme again,by just calling the OSWord.

KNOWN PROBLEMS/FUTURE ENHANCEMENTS-
No known problems

HISTORY-
V0.90 Original developement version
V1.00 Released to EUG,having fixed a problem with frame sync on proper
      computer monitors (it was previously only tried on a domestic TV).
V1.15 Screen blanking does not interfer with the VDU queue,which could cause
      problems if the screen saver kicked in half way through PRINTing text.
      Adjusted osword block to ensure it is passed accross the Tube correctly