Commodore 64 Uživatelský manuál stáhnout pdf (Strana 52)

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.

"POKE53265,PEEK(53265)AND 239

To bring back the screen, use the POKE shown below:

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

($DOI2). 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 made 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 w.ritten 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 ($DO19) is

turned ON by setting it to 1.

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

150 PROGRAMMING GRAPHICS

1 2 ... 47 48 49 50 51 52 53 54 55 56 57 ... 82 83

Žádné komentáře

Commodore 64 Uživatelský manuál Strana 52