Auto Fade for the TS-2068

The April 1986 issue of Your Sinclair had an article and a program listing for a feature which provides for a screen black-out if you don’t do anything for a while. It has an adjustable time-out interval of up to 20 minutes.

I found that the program works equally well on the TS2068 and with the Spectrum ROM.

The program works as follows. After a timed interval in which no computer keys are pressed, the screen attributes are moved and stored in upper memory, and the attributes area of memory is filled with zeros, giving a black screen. The border is also blacked out. At the same time a flashing white square located in the lower right-hand corner of the screen is displayed as a reminder.

Whenever a key is touched the screen attributes are restored and presto, the screen reappears.

The code occupies a space of about 1200 bytes of upper RAM. The code itself is only about 120 bytes, however space is required to store the 768 bytes of the screen attributes.

This location has been carefully chosen so that the interrupt mode (IM2) which it uses will not be disturbed by computer peripherals. I checked, and its operation is not affected by the Larken disk system. Also, the code does not affect the user-defined graphics area of memory.

The article mentions that because of the peculiarity of the IM2 interrupt mode only the brave, or maybe the foolhardy, would attempt to relocate it.

The easiest way to use this utility would be to load the Basic each time, and have it POKE the code into place. This allows you to select the time delay interval desired.

If you can settle for a standard time interval then saving the code and reloading it for each use is entirely practical. In this case you would initialize the feature with RAND USR 64967.

To turn off the feature use RAND USR 64994.