4-16
MPC106 PCIB/MC User's Manual
MOTOROLA
4.3.3 Address Transfer Termination
Address transfer termination occurs with the assertion of the address acknowledge (AACK)
signal. A snoop response is indicated by the assertion of the ARTRY signal until one clock
after AACK; the bus clock cycle after AACK is referred to as the ARTRY window. The
MPC106 controls assertion of AACK unless the cycle is claimed by the external L2 cache
controller (as indicated by the assertion of the HIT signal by the L2 cache controller).
Following assertion of HIT, the L2 cache controller is responsible for assertion of AACK.
When AACK is asserted by the L2 cache controller, it should be asserted for one clock
cycle, and then negated for one clock cycle prior to entering a high-impedance state. The
MPC106 holds the AACK signal in a high-impedance state until assertion of AACK by the
MPC106 is required for the termination of the address cycle. For address bus transactions
initiated by a processor, the snoop response originates from either the MPC106 or an
alternate bus master (the other processors or an external L2 cache controller). For
transactions initiated by the MPC106, the snoop response originates from an alternate bus
master.
Table 4-6. Misaligned Data Transfers (4-Byte Examples)
Transfer Size
(Four Bytes)
TSIZ[0–2]
A[29–31]
Data Bus Byte Lanes
0
1
2
3
4
5
6
7
Aligned
1 0 0
0 0 0
A
A
A
A
—
—
—
—
Misaligned—first access
second access
0 1 1
0 0 1
—
A
A
A
—
—
—
—
0 0 1
1 0 0
—
—
—
—
A
—
—
—
Misaligned—first access
second access
0 1 0
0 1 0
—
—
A
A
—
—
—
—
0 1 1
1 0 0
—
—
—
—
A
A
—
—
Misaligned—first access
second access
0 0 1
0 1 1
—
—
—
A
—
—
—
—
0 1 1
1 0 0
—
—
—
—
A
A
A
—
Aligned
1 0 0
1 0 0
—
—
—
—
A
A
A
A
Misaligned—first access
second access
0 1 1
1 0 1
—
—
—
—
—
A
A
A
0 0 1
0 0 0
A
—
—
—
—
—
—
—
Misaligned—first access
second access
0 1 0
1 1 0
—
—
—
—
—
—
A
A
0 1 0
0 0 0
A
A
—
—
—
—
—
—
Misaligned—first access
second access
0 0 1
1 1 1
—
—
—
—
—
—
—
A
0 1 1
0 0 0
A
A
A
—
—
—
—
—
Notes
:
A:
—
:
Byte lane not used
Byte lane used