Commodore 64 Uživatelský manuál stáhnout pdf (Strana 22)

EXTENDED BACKGROUND COLOR MODE

Extended background color mode gives you control over the back-

ground color of each individual character, as well as over the fore-

ground color. For example, in this mode you could display a blue char-

acter with a yellow background on a white screen.

There are 4 registers available for extended background color mode.

Each of the registers can be set to any of the 16 colors.

Color memory is used to hold the foreground color in extended back-

ground mode. It is used the same as in standard character mode.

Extended character mode places a limit on the number of different

characters you can display, however. When extended color mode is on,

only the first 64 characters in the character ROM (or the first 64 char-

acters in your programmable character set) can be used. This is be-

cause two of the bits of the character code are used to select the back-

ground color. It might work something like this:

The character code (the number you would POKE.to the. screen) of the

letter "A" is a 1. When extended color mode is on, if you POKEd a 1 to

the screen, an "A" would appear. If you POKEd a 65 to the screen

normally, you would expect the character with character code (CHR$)

129 to appear, which is a reversed "A." This does NOT happen in ex-

tended color mode. Instead you get the same unreversed "A" as before,

but on a different background color. The following chart gives the

codes:

Extended color mode is turned ON by setting bit 6 of the VIC-II regis-

ter to a .1at location 53265 ($D011 in HEX). The following POKE does it:

POKE 53265, PEEK(53265)OR 64

120 PROGRAMMING GRAPHICS

CHARACTERCODE BACKGROUND COLOR REGISTER

RANGE

BIT 7 BIT 6

NUMBER ADDRESS

0-63 0 0 0

53281 ($D021)

64-127 0 1 1

53282 ($D022)

128-191

0 2

53283 ($D023)

192-255 1 1

53284 ($D024)

1 2 ... 17 18 19 20 21 22 23 24 25 26 27 ... 82 83

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Commodore 64 Uživatelský manuál Strana 22