External Bus Interface
MPC885 PowerQUICC Family Reference Manual, Rev. 2
13-4
Freescale Semiconductor
BURST
Burst Transfer
1
O
Driven by the MPC885 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
Sampled by the MPC885 when an external device initiates a transaction and the
memory controller was configured to handle external master accesses.
TSIZ[0:1]
Transfer Size
2
O
Driven by the MPC885 along with the address when it owns the external bus. Specifies
the data transfer size for the transaction.
I
Sampled by the MPC885 when an external device initiates a transaction and the
memory controller was configured to handle external master accesses.
AT[0:3]
Address Type
4
O
Driven by the MPC885 along with the address when it owns the external bus. Indicates
additional information about the address on the current transaction.
RSV
Reservation
Transfer
1
O
Driven by the MPC885 along with the address when it owns the external bus. Indicates
additional information about the address on the current transaction.
PTR
Program Trace
1
O
Driven by the MPC885 along with the address when it owns the external bus. Indicates
additional information about the address on the current transaction.
BDIP
Burst Data in
Progress
1
O
Driven by the MPC885 when it owns the external bus as part of the burst protocol.
Asserted indicates that the second beat in front of the current one is requested by the
master. Negated before the burst transfer ends to abort the burst data phase.
Transfer Start
TS
Transfer Start
1
O
Driven by the MPC885 when it owns the external bus. Indicates the start of a transaction
on the external bus.
I
Sampled by the MPC885 when an external device initiates a transaction and the
memory controller was configured to handle external master accesses.
STS
Special Transfer
Start
1
O
Driven by the MPC885 when it owns the external bus. Indicates the start of a transaction
on the external bus or signals the beginning of an internal transaction in show cycle
mode.
Reservation Protocol
KR/RETRY
Kill Reservation/
Retry
1
I
If the core initiates a bus cycle by executing a
stwcx
. to a nonlocal bus on which the
memory reservation is lost, the nonlocal bus uses this signal to back-off the cycle. See
Section 13.4.9, “Memory Reservation.”
For regular transactions, the slave device drives this signal to indicate that the MPC885
must relinquish the bus and retry the cycle.
Table 13-1. MPC885 Signal Overview (continued)
Signal Pins
I/O
1
Description
Summary of Contents for PowerQUICC MPC870
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