Altera External Memory PHY Interface - Manual (Page 74)

4–6 Chapter 4: Support for Arria GX, HardCopy II, Stratix II, and Stratix II GX Devices
DDR2/DDR SDRAM
External Memory PHY Interface (ALTMEMPHY) (nonAFI) Megafunction User Guide © January 2010 Altera Corporation
PLL Reconfiguration
The ALTMEMPHY MegaWizard interface automatically generates the PLL
reconfiguration block by instantiating an ALTPLL_RECONFIG variation for Stratix II
and Stratix II GX devices to match the generated ALTPLL megafunction instance. The
ALTPLL_RECONFIG megafunction varies the resynchronization clock phase and the
measure clock phase.
Half-rate
and full rate mem_clk_ext_2x C3 > 0

Full-Rate Dedicated This clock is only used if
the memory clock
generation uses dedicated
output pins. Applicable
only in HardCopy II or
Stratix II prototyping for
HardCopy II designs.
Half-rate
and full rate resync_clk_2x C4 Calibrated Full-Rate Regional Clocks the
resynchronization
registers after the capture
registers. Its phase is
adjusted to the center of
the data valid window
across all the
DQS-clocked DDIO
groups.
Half-rate
and full rate measure_clk_2x C5 Calibrated Full-Rate Regional (2) This clock is for VT
tracking. This free-running
clock measures relative
phase shifts between the
internal clock(s) and those
being fed back through a
mimic path. As a result,
the ALTMEMPHY
megafunction can track
VT effects on the FPGA
and compensate for the
effects.
Half-rate
and full rate ac_clk_2x — 0,
90 ,180,
270 
Full-Rate Global The ac_clk_2x clock is
derived from either
mem_clk_2x
(when you
choose 0  or 180 phase
shift) or
write_clk_2x
(when
you choose 90
 or 270
phase shift).
Notes to Table 4–1 :
(1) In full-rate designs a _1x clock may run at full-rate clock rate.
(2) This clock should be of the same clock network clock as the resync_clk_2x clock.
Table 4–1. DDR2/DDR SDRAM Clocking in Arria GX, HardCopy II, Stratix II, and Stratix II GX Devices (Part 2 of 2)
Design
Rate Clock Name
Postscale
Counter
Phase
(Degrees) Clock Rate
Clock
Network Type Notes