Commodore 64 Uživatelský manuál stáhnout pdf (Strana 6)

on the keyboard. One of the features of the Commodore 64 is the ability

to use patterns located in RAM memory. These RAM patterns are

created by you, and that means that you can have an almost infinite set

of symbols for" games, business applications, etc.

A normal character set contains 256 characters in which each c.har-

acter is defined by 8 bytes of data. Since each character takes up 8

bytes this means that a full character set is 256*8=2K bytes of memory.

Since the VIC-II chip looks at 16K of memory at a time, there are 8

possible locations for a complete character set. Naturally, you are free

to use less than a full character set. However, it must still start at one of

the 8 possible starting locations.

The location of character memory is controlled by 3 bits of the VIC-II

control register located at 53272 ($DOI8 in HEX notation). Bits 3,2, and

1 control where the characters' set is located in 2K blocks. Bit 0 is ig-

nored. Remember that this is the same register that deterrt.ines where

screen memory is located so avoid disturbing the screen memory bits. To

change the location of character me{T1ory,the following BASIC state-

ment can be used:

POKE 53272,(PEEK(53272)AND240)OR A

Where A is one of the following values:

'Remember to add in the BANKaddress.

104 PROGRAMMING GRAPHICS

VALUEI

LOCATION OF CHARACTER MEMORY*

BITS

of A

DECIMAL

HEX

XXXXOOOX 0

$0000-$07FF

2 XXXXOOIX 2048

$0800-$OFFF

XXXXOI0X 4096

$1000-$17FF

ROM IMAGE in BANK

o & 2 (default)

XXXXOIIX

6144

$1800-$1 FFF

ROM IMAGE in BANK

0&2

XXXX 1 OOX 8192

$2000-$27FF

10 XXXXI0IX 10240

$2800-$2FFF

12 XXXXII0X 12288

$3000-$37FF

XXXXIIIX

14336 $3800-$3FFF

1 2 3 4 5 6 7 8 9 10 11 ... 82 83

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