Motorola MC68020 User Manual

5- 6 M68020 USER’S MANUAL MOTOROLA
OP0
OP1
OP2
OP3
31
0
15
0
OP2
OP3
7
0
LONG-WORD OPERAND
WORD OPERAND
BYTE OPERAND
OP3
Figure 5-3. Internal Operand Representation
Figure 5-4 shows the required organization of data ports on the MC68020/EC020 bus for
8-, 16-, and 32-bit devices. The four bytes shown in Figure 5-4 are connected through the
internal data bus and data multiplexer to the external data bus. This path is the means
through which the MC68020/EC020 supports dynamic bus sizing and operand
misalignment. Refer to 5.2.2 Misaligned Operands for the definition of misaligned
operand. The data multiplexer establishes the necessary connections for different
combinations of address and data sizes.
0
1
2
3
ROUTING AND DUPLICATION
BYTE 0
BYTE 2
BYTE 1
BYTE 3
16-BIT PORT
REGISTER
MULTIPLEXER
EXTERNAL DATA BUS
ADDRESS
xxxxxxx0
xxxxxxx0
2
INCREASING
MEMORY
A
DDRESSE
S
D31– D24
D23–D16
D15–D8
D7–D0
BYTE 0
BYTE 1
BYTE 2
BYTE 3
BYTE 0
BYTE 1
BYTE 2
BYTE 3
8-BIT PORT
2
3
1
xxxxxxx0
EXTERNAL BUS
INTERNAL TO
THE MC68020/EC02
0
32-BIT PORT
OP0
OP1
OP2
OP3
Figure 5-4. MC68020/EC020 Interface to Various Port Sizes

Motorola MC68020 Specifications

General

Brand	Motorola
Model	MC68020
Category	Computer Hardware
Language	English