9-4
MPC561/MPC563 Reference Manual
MOTOROLA
Bus Interface Signal Descriptions
9.4
Bus Interface Signal Descriptions
Table 9-1 describes each signal in the bus interface unit. More detailed descriptions can be
found in subsequent subsections. The buses are described in big endian manner, which
means that bit 0 is the most significant bit in a bus (MSB), and bit 31 is the least significant
bit (LSB).
.
Table 9-1. MPC561/MPC563 BIU Signals
Signal Name
Pins
Active
I/O
Description
Address and Transfer Attributes
ADDR[8:31]
Address bus
24
[8:31]
High
O
Specifies the physical address of the bus transaction.
I
Driven by an external bus master when it owns the
external bus. An input for testing purposes only.
RD/WR
Read/write
1HIgh
O
Driven by the MPC561/MPC563 along with the
address when it owns the external bus. Driven high
indicates that a read access is in progress. Driven low
indicates that a write access is in progress.
I
Driven by an external master when it owns the external
bus. Driven high indicates that a read access is in
progress. Driven low indicates that a write access is in
progress.
BURST
Burst transfer
1Low
O
Driven by the MPC561/MPC563 along with the
address when it owns the external bus. Driven low
indicates that a burst transfer is in progress. Driven
high indicates that the current transfer is not a burst.
I
Driven by an external master when it owns the external
bus. Driven low indicates that a burst transfer is in
progress. Driven high indicates that the current
transfer is not a burst. The MPC561/MPC563 does not
support burst accesses to internal slaves.
TSIZ[0:1]
Transfer size
2High
O
Driven by the MPC561/MPC563 along with the
address when it owns the external bus. Specifies the
data transfer size for the transaction.
I
Driven by an external master when it owns the external
bus. Specifies the data transfer size for the
transaction.
AT[0:3]
Address type
3High
O
Driven by the MPC561/MPC563 along with the
address when it owns the external bus. Indicates
additional type on the current transaction.
I
Only for testing purposes.
RSV
Reservation transfer
1Low
O
Driven by the MPC561/MPC563 along with the
address when it owns the external bus. Indicates
additional information about the address on the
current transaction.
I
Only for testing purposes.