HC4GX15 Datasheet, PDF (89/668 Pages) Altera Corporation – HardCopy IV Device Handbook

Chapter 7: External Memory Interfaces in HardCopy IV Devices
7–23
HardCopy IV External Memory Interface Features
HardCopy IV External Memory Interface Features
HardCopy IV devices are rich with features that allow robust high-performance
external memory interfacing. The ALTMEMPHY megafunction allows you to set
these external memory interface features and helps set up the physical interface
(PHY) best suited for your system.
This section describes each HardCopy IV device feature that is used in external
memory interfaces from the DQS phase-shift circuitry, DQS logic block, leveling
multiplexers, dynamic OCT control block, IOE registers, IOE features, and the PLL.
1 When using the Altera^® memory controller MegaCore^® functions, the PHY is
instantiated for you.
1 The ALTMEMPHY megafunction and the Altera memory controller MegaCore
functions can run at half the frequency of the I/O interface of the memory devices to
allow better timing management in high-speed memory interfaces. HardCopy IV
devices have built-in registers to convert data from full-rate (I/O frequency) to
half-rate (controller frequency) and vice versa. You can bypass these registers if your
memory controller is not running at half the rate of the I/O frequency.
f For more information about the ALTMEMPHY megafunction, refer to the External
DDR Memory PHY Interface Megafunction User Guide (ALTMEMPHY).
DQS Phase-Shift Circuitry
The HardCopy IV phase-shift circuitry provides phase shift to the DQS and CQn pins
on read transactions when the DQS and CQn pins are acting as input clocks or strobes
to the HardCopy IV device. The DQS phase-shift circuitry consists of DLLs that are
shared between multiple DQS pins and the phase-offset module to further fine-tune
the DQS phase shift for different sides of the device. Figure 7–15 shows how the DQS
phase-shift circuitry is connected to the DQS and CQn pins in the device.
© January 2010 Altera Corporation
HardCopy IV Device Handbook, Volume 1