MSC8144E Reference Manual, Rev. 3
15-10
Freescale
Semiconductor
PCI
occur because no buffer entries are available in the I/O sequencer, or the sixteen clock latency
timer has expired without transfer of the first data. The target latency timer of the VCOP can be
optionally disabled (see page 15-33
).
When the VCOP is in agent mode and the CFG_LOCK — configuration lock bit is set (see
page 15-33 for details) the VCOP will retry all transactions to the PCI Configuration Space or the
internal (on-chip) memory-mapped register space. Note that all retried accesses need to be
completed. An example of a retry is shown in Figure 15-5.
Note that because a target can determine whether or not data is transferred (when both
PCI_IRDY
and
PCI_TRDY
are asserted), if it wants to do only one more data transfer and then stop, it may
assert
PCI_TRDY
and
PCI_STOP
at the same time.
Target-abort refers to the abnormal termination that is used when a fatal error has occurred, or
when a target will never be able to respond. Target-abort is indicated when
PCI_STOP
is asserted
and
PCI_DEVSEL
is deasserted. This indicates that the target requires the transaction to be
terminated and does not want the transaction tried again. Note that any transferred data may have
been corrupted.
If the VCOP is the intended target of a transaction and an address parity error occurs, or a data
parity error occurs on a write transaction to system memory, it continues the transaction on the
PCI bus but aborts internally. The VCOP does not target-abort in this case.
If the VCOP is initiating a transaction and the transaction terminates with a target-abort,
undefined data will be returned on a read and write data will be lost. An example of a target-abort
is shown in Figure 15-5.
An initiator may retry any target disconnect accesses, except target-abort, at a later time starting
with the address of the next non-transferred data. Retry is actually a special case of disconnect
where no data transfer occurs at all and the initiator must start the entire transaction over again.
15.1.8.3 Other Bus Operations
The following sections provide information on additional PCI bus operations.
15.1.8.3.1 Fast Back-to-Back Transactions
In the two types of fast back-to-back transactions, the first type places the burden of avoiding
contention on the initiator while the second places the burden on all potential targets. The VCOP
as a target supports both types of fast back-to-back transactions but does not support them as an
initiator. The VCOP as a target has the fast back-to-back enable bit hardwired to one, that is,
enabled.
For the first type (governed by the initiator), the initiator may only run a fast back-to-back
transaction to the same target. For the second type, when the VCOP detects a fast-back-to-back
Summary of Contents for MSC8144E
Page 1: ...MSC8144E Reference Manual Quad Core Media Signal Processor MSC8144ERM Rev 3 July 2009 ...
Page 48: ...MSC8144E Reference Manual Rev 3 xlviii Freescale Semiconductor ...
Page 86: ...MSC8144E Reference Manual Rev 3 1 38 Freescale Semiconductor Overview ...
Page 168: ...MSC8144E Reference Manual Rev 3 3 60 Freescale Semiconductor External Signals ...
Page 242: ...MSC8144E Reference Manual Rev 3 5 26 Freescale Semiconductor Reset ...
Page 314: ...MSC8144E Reference Manual Rev 3 8 24 Freescale Semiconductor General Configuration Registers ...
Page 414: ...MSC8144E Reference Manual Rev 3 10 14 Freescale Semiconductor MSC8144E SC3400 DSP Subsystem ...
Page 452: ...MSC8144E Reference Manual Rev 3 11 38 Freescale Semiconductor Internal Memory Subsystem ...
Page 520: ...MSC8144E Reference Manual Rev 3 12 68 Freescale Semiconductor DDR SDRAM Memory Controller ...
Page 1070: ...MSC8144E Reference Manual Rev 3 21 28 Freescale Semiconductor Timers ...