Motorola MC68020 User Manual page 57

Table 5-5 lists the combinations of SIZ1, SIZ0, A1, and A0 and the corresponding pattern
of the data transfer for write cycles from the internal multiplexer of the MC68020/EC020 to
the external data bus.
Table 5-5. MC68020/EC020 Internal to External Data Bus
Transfer
Size
Byte
Word
3 Bytes
Long Word
*
Due to the current implementation, this byte is output but never used.
x = Don't care
NOTE: The OP tables on the external data bus refer to a particular byte of the operand that
is written on that section of the data bus.
MOTOROLA
Multiplexer—Write Cycles
Size Address
SIZ1 SIZ0 A1 A0
0 1 x x
x 0
1 0
x 1
1 0
1 1 0 0
1 1 0 1
1 1 1 0
1 1 1 1
0 0 0 0
0 0 0 1
0 0 1 0
0 0 1 1
M68020 USER'S MANUAL
External Data Bus
Connection
D31–D24
D23–D16 D15–D8
OP3 OP3 OP3
OP2
OP2 OP3
OP2 OP2 OP3
OP1 OP2 OP3
OP1 OP1 OP2
OP2 OP1
OP1
*
OP1 OP1 OP2
OP0 OP1 OP2
OP0 OP0 OP1
OP1 OP0
OP0
*
OP0 OP0 OP1
D7–D0
OP3
OP3
OP2
*
OP0
OP3
OP2
OP1
OP3
OP2
OP1
OP0
5- 9