OTHER GRAPHICS FEATURES

SCREEN BLANKING

Bit 4 of the VIC-II control register controls the screen blanking func- tion. It is found in the control register at location 53265 ($D011). When it is turned ON (in other words, set to a 1) the screen is normal. When bit 4 is set to 0 (turned OFF), the entire screen changes to border color.

The following POKE blanks the screen. No data is lost, it just isn't displayed.

   POKE 53265,PEEK(53265)AND 239

   POKE 53265,PEEK(53265)OR 16

NOTE: Turning off the screen will speed up the processor slightly. This means that program RUNning is also sped up.

RASTER REGISTER

The raster register is found in the VIC-II chip at location 53266 ($D012). The raster register is a dual purpose register. When you read this register it returns the lower 8 bits of the current raster position. The raster position of the most significant bit is in register location 53265 ($D011). You use the raster register to set up timing changes in your display so that you can get rid of screen flicker. The changes on your screen should be mode when the raster is not in the visible display area, which is when your dot positions fall between 51 and 251.

When the raster register is written to (including the MSB) the number written to is saved for use with the raster compare function. When the actual raster value becomes the same as the number written to the raster register, a bit in the VIC-II chip interrupt register 53273 ($D019) is turned ON by setting it to 1.

NOTE: If the proper interrupt bit is enabled (turned on), an interrupt (IRQ) will occur.