2–160
Altera Corporation
Stratix II GX Device Handbook, Volume 2
October 2007
Native Modes
PIPE Mode Default Settings
In the PIPE mode default settings, the receiver PLL is in automatic lock
mode. The PLL moves from lock to reference mode to lock to data mode
based on the
rx_freqlocked
being asserted. For the
rx_freqlocked
signal to be asserted, the CRU PLL clock should be within the PPM
threshold settings of the CRU reference clock.
The PPM detector checks the PPM threshold settings by comparing the
CRU PLL clock output with the reference clock for approximately 32768
clock cycles. For a 250 MHz PLD interface clock frequency, this
comparison time period exceeds 4 us, which violates the PCI-E
specification. The NTFS soft IP overcomes the restriction.
Enable Fast Recovery Mode Option
When you select the
Enable fast recovery mode
option, consider the
following:
■
NFRI is created in the PLD side for each PCI-E channel
■
NFRI is a soft IP, so it consumes logic resources
■
This block is self-contained, so no input/output ports are available to
access the soft IP
The NFRI takes control of the
rx_locktorefclk
and
rx_locktodata
signals on the ALT2GXB transceiver and therefore avoids the delay of the
PPM detector discussed in
“PIPE Mode Default Settings” on page 2–160
.
1
If you select the
rx_locktorefclk
and
rx_locktodata
signals in the MegaWizard Plug-In Manager, the
Enable fast
recovery mode
option cannot be used.
NTFS Fast Recovery IP (NFRI) in Software Versions before
Quartus II 7.2
This section discusses the solution to control the sequence of events
around the results of the 4 us timing requirement during the P0s to P0
state transition. This is only applicable for software versions before
Quartus II 7.2 with the transceiver channel configured in PCI Express
(PIPE) mode and the optional
fast recovery mode
enabled in the
ALT2GXB MegaWizard. Use this for synchronous and non-synchronous
PCI Express (PIPE) modes. The solution requires that you use the data in
user logic in the core only if the data is valid.
1
In the Quartus II software version 7.2, the solution is built into
the software when you enable the
fast recovery mode
option
in
the ALT2GXB MegaWizard.
Содержание Stratix II GX
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