Motorola M68000 Betriebsanweisung PDF herunterladen (Seite 22)

8 Assembly Language Programming for the 68000 Family

Hexadecimal

Hexadecimal, or base 16, uses positional values that are powers of 16.

Each hex digit can take on 16 values. Since the decimal digits 0 through

9 only represent 10 values, 6 additional symbols are needed. The letters

A through F are used to represent these additional values. Thus the hex

digits are represented by 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, and F,

corresponding to the values from 010 to 1510. The positional values are:

(16)° • l

(16)* * 16

(16)2 * 256

(16)3 = 4096

etc.

As you can see, these values increase rapidly. A hex number is usually

larger than it looks. For example, 32BF10 is

3(16)3+2 (16)2+ll(16)1+15(16)0

- 12,288+512+176+15 = 12,99110

We can convert from decimal to hexadecimal by either method dis

cussed above. For example, to convert 38710 to hex, we perform the

following:

387/16 « 24 R 3

24/16 » 1 R 8

1/16 >0R1 (finished)

The result in hex is 183ie. Remember to list the hex digits in reverse order.

A nice property of hexadecimal numbers is that they can be converted

to binary almost by inspection. Since 24=16, there is a simple relationship

present. Four binary digits grouped together can represent one hexadeci

mal digit. The binary values 0000 through 1111 represent the hexadecimal

digits 0 through F.

HEX

BINARY HEX

BINARY

0 0000

1000

0001

9 1001

0010

1010

0011 B

1011

0100

1100

0101

1101

0110 E

1110

0111

P 1111

1 2 ... 17 18 19 20 21 22 23 24 25 26 27 ... 255 256

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