
7-2
MPC105 PCIB/MC User's Manual
MOTOROLA
the MPC105 can accept the burst-read transfer. When the MPC105 is granted the PCI bus,
the burst-write transaction continues.
As a master, the MPC105 supports read and write operations to the PCI memory space, the
PCI I/O space, and the PCI 256-byte configuration space. The MPC105 also supports PCI
special cycles and interrupt acknowledge cycles. As a target, the MPC105 supports read and
write operations to system memory.
Buffers are provided for operations between the PCI bus and the 60x processor or system
memory. Processor read and write operations each have a 32-byte buffer, and memory
operations have one 32-byte read buffer and two 32-byte write buffers. See Section 8.1,
“Internal Control,” for more information.
The interface can be programmed for either little-endian or big-endian formatted data, and
provides the data swapping, byte enable swapping, and address translation in hardware. See
Appendix B, “Bit and Byte Ordering,” for more information on the bi-endian features of
the MPC105.
7.1.1 The MPC105 as a PCI Master
Upon detecting a 60x-to-PCI transaction, the MPC105 requests the use of the PCI bus. For
write operations to the PCI bus, the MPC105 requests the PCI bus when the 60x completes
the write operation on the 60x processor bus. For read operations from the PCI bus, the
MPC105 requests the PCI bus when it decodes that the access is for PCI address space.
Once granted, the MPC105 drives the 32-bit PCI address (AD31–AD0) and the 4-bit bus
command (C/BE3–C/BE0) signals. The master interface supports reads and writes of up to
32-bytes without inserting master-initiated wait states.
The master part of the interface can initiate master-abort cycles, recognizes target-abort,
target-retry, and target-disconnect cycles, and supports various device selection timings.
The master interface does not run fast back-to-back or interlocked accesses.
7.1.2 The MPC105 as a PCI Target
As a target, upon detection of a PCI address phase the MPC105 decodes the address and
bus command to determine if the transaction is for system memory. If the transaction is
destined for system memory, the target interface latches the address and decode the
command and forwards them to an internal control unit. On writes to system memory, data
is forwarded along with the byte enables to the internal control unit. On reads, four bytes
of data are provided to the PCI bus and the byte enables determine which byte lanes contain
valid data.
The target interface of the MPC105 can issue target-abort, target-retry, and target-
disconnect cycles. Also, The target interface supports fast back-to-back transactions, and
interlocked accesses using the PCI lock protocol.