Altera PCI Compiler Manual de usuario Pagina 95

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Altera Corporation User Guide Version 11.1 3–21
October 2011
Functional Description
lt_rdyn
Input Low
Local target ready. The local side asserts
lt_rdyn to indicate
a valid data input during target read, or ready to accept data
input during a target write. During a target read,
lt_rdyn
deassertion suspends the current transfer (i.e., a wait state is
inserted by the local side). During a target write, an inactive
lt_rdyn signal directs the PCI MegaCore function to insert
wait states on the PCI bus. The only time the function inserts
wait states during a burst is when
lt_rdyn inserts wait states
on the local side.
lt_rdyn is sampled one clock cycle before actual data is
transferred on the local side. During target write transactions,
lt_rdyn has also special functionality. To allow the local side
ample time to issue a retry for the write cycle, the PCI
MegaCore function does not assert
trdyn in the first data
phase unless the local side asserts
lt_rdyn. In this case, the
local side asserts
lt_rdyn to indicate that it intends to
complete at least one data phase and it is not going to issue a
retry.
Refer to the “Additional Design Guidelines for Target
Transactions” on page 3–88 section for additional information
about the
lt_rdyn functionality.
lt_framen
Output Low
Local target frame request. The
lt_framen output is
asserted while the PCI MegaCore function is requesting
access to the local side. It is asserted one clock cycle before
the function asserts
devseln, and it is released after the last
data phase of the transaction is transferred to/from the local
side.
lt_ackn
Output Low
Local target acknowledge. The PCI function asserts
lt_ackn
to indicate valid data output during a target write, or ready to
accept data during a target read. During a target read, an
inactive
lt_ackn indicates that the function is not ready to
accept data and local logic should delay the bursting operation.
During a target write,
lt_ackn de-assertion suspends the
current transfer (i.e., a wait state is inserted by the PCI master).
The
lt_ackn signal is only inactive during a burst when the
PCI bus master inserts wait states.
lt_dxfrn
Output Low Local target data transfer. The PCI MegaCore function asserts
the
lt_dxfrn signal when a data transfer on the local side is
successful during a target transaction.
Table 3–7. Target Signals Connecting to the Local Side (Part 2 of 3)
Name Type Polarity Description
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