Commodore 64 Instrukcja Użytkownika Pobierz pdf (Strona 24)

8K section of memory on the TV screen. When in bit map mode, you can

directly control whether an individual dot on the screen is on or off.

There are two types of bit mapping available on the Commodore 64.

They are:

1) Standard (high-resolution) bit mapped mode (320-dot by 200-dot

resolution)

2) Multi-color bit mapped mode (160-dot by 200-dot resolution)

Each is very similar to the character type it is named for: standard has

greater resolution, but fewer color selections. On the other hand, multi-

color bit mapping trades horizontal resolution for a greater number of

colors in an 8-dot by a-dot square.

STANDARD HIGH-RESOLUTION BIT MAP MODE

Standard bit map mode gives you a 320 horizontal dot by 200 vertical

dot resolution, with a choice of 2 colors in each 8-dot by 8-dot section.

Bit map mode is selected (turned ON) by setting bit 5 of the VIC-II

control register to a 1 at location 53265 ($DOll in HEX). The following

POKE will do this:

POKE 53265,PEEK(53265)OR 32

Bit map mode is turned OFF by setting bit 5 of the VIC-II control

POKE 53265,PEEK(53265)AND 223

Before we get into the details of the bit map mode, there is one more

issue to tackle, and that is where to locate the bit map area.

HOW IT WORKS

If you remember the

PROGRAMMABLECHARACTERSsection you will

recall that you were able to set the bit pattern of a character stored in

RAMto almost anything you wanted. If at the same time you change the

character that is displayed on the screen, you would be able to change

a single dot, and watch it happen. This is the basis of bit-mapping. The

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Commodore 64 Instrukcja Użytkownika Strona 24