HC4GX15 Datasheet, PDF (104/668 Pages) Altera Corporation – HardCopy IV Device Handbook

7–38
Chapter 7: External Memory Interfaces in HardCopy IV Devices
HardCopy IV External Memory Interface Features
Similarly, the resynchronization clock feeds the read-leveling circuitry to produce the
optimal resynchronization and postamble clock for each DQS/DQ group in the
calibration process. The resynchronization and postamble clocks can use different
clock outputs from the leveling circuitry. The output from the read-leveling circuitry
can also generate the half-rate resynchronization clock that goes to the core fabric.
f
The ALTMEMPHY megafunction calibrates the alignment for read and write leveling
dynamically during the initialization process. For more information about the
ALTMEMPHY megafunction, refer to the External DDR Memory PHY Interface
Megafunction User Guide (ALTMEMPHY).
Dynamic On-Chip Termination Control
Figure 7–26 shows the dynamic OCT control block. The block includes all the registers
required to dynamically turn OCT on during a read and turn OCT off during a write.
f For more information about OCT, refer to “OCT” on page 7–41, or to the HardCopy IV
Device I/O Features chapter.
Figure 7–26. HardCopy IV Dynamic OCT Control Block
OCT Control
2
OCT Half-
DFF
Rate Clock
OCT Enable
DFF
HDR
Block
Resynchronization
Registers
OCT Control Path
Write
Clock (1)
Note to Figure 7–26:
(1) The write clock comes from either the PLL or the write-leveling delay chain.
I/O Element Registers
The IOE registers have been expanded to allow source-synchronous systems to have
faster register-to-register transfers and resynchronization. Both top, bottom, left, and
right IOEs have the same capability, although left and right IOEs have extra features
to support LVDS data transfer.
Figure 7–27 shows the registers available in the HardCopy IV input path. The input
path consists of the DDR input registers, resynchronization registers, and HDR block.
You can bypass each block of the input path.
HardCopy IV Device Handbook, Volume 1
© January 2010 Altera Corporation