2–66
Altera Corporation
Stratix II GX Device Handbook, Volume 2
October 2007
Receiver Modules
Manual Lock Options
Two optional input pins (
rx_locktorefclk
and
rx_locktodata
)
allow you to control whether the CRU PLL automatically or manually
switches between lock-to-reference mode and lock-to-data modes. This
enables you to bypass the default automatic switchover circuitry if either
rx_locktorefclk
or
rx_locktodata
is instantiated.
When the
rx_locktorefclk
signal is asserted, it forces the CRU PLL to
lock to the reference clock (
rx_cruclk
). Asserting
rx_locktodata
forces
the CRU PLL to lock to data. This occurs whether the CRU is ready or not.
When both signals are asserted, the
rx_locktodata
signal takes
precedence over the
rx_locktorefclk
signal.
The signal loss threshold detector, PPM threshold frequency detector, and
phase relationship detector reaction times may be too long for some
applications. You can manually control the CRU to reduce CRU lock
times using the
rx_locktorefclk
and
rx_locktodata
ports. Using
the manual mode may reduce the time it takes for the CRU to switch from
lock-to-reference mode to lock-to-data mode. You can assert the
rx_locktorefclk
to initially train the CRU. The
rx_locktodata
signal should be asserted after training the CRU.
When the
rx_locktorefclk
signal is asserted, the
rx_freqlocked
signal does not have any significance because it is low, indicating that the
CRU is in lock-to-reference mode. If lock-to-data mode is asserted, the
rx_freqlocked
signal is always asserted, indicating that the CRU is in
lock-to-data mode. When both signals are asserted, lock-to-data mode
takes precedence. If both signals are deasserted, the CRU switchover is in
automatic mode.
Table 2–17
shows a summary of the control signals.
Deserializer
The deserializer block converts incoming high-speed serial data streams
to 8-, 10-, 16-, or 20-bit-wide parallel data synchronized to the recovered
clock of the CRU. Use the 8- and 10-bit operations, which support a data
rate from 600 Mbps to 3.125 Gbps, in the single-width mode. Use the
16- and 20-bit operations, which support a data rate from 1 Gbps to
6.375 Gbps, for the double-width mode.
Table 2–17. CRU User Control Lock Signals
rx_locktorefclk
rx_locktodata
CRU Mode
1
0
Lock-to-reference clock
x
1
Lock to data
0
0
Automatic
Содержание Stratix II GX
Страница 640: ...4 244 Altera Corporation Stratix II GX Device Handbook Volume 2 October 2007 Document Revision History ...
Страница 642: ...4 246 Altera Corporation Stratix II GX Device Handbook Volume 2 October 2007 Document Revision History ...
Страница 672: ...6 14 Altera Corporation Stratix II GX Device Handbook Volume 2 October 2007 Document Revision History ...