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1.1. ALTDDIO Features
1.2. ALTDDIO Common Applications
1.3. ALTDDIO Resource Utilization and Performance
1.4. ALTDDIO Parameter Settings
1.5. ALTDDIO Functional Description
1.6. Design Example: 8-Bit DDR Divider Using ALTDDIO_BIDIR
1.7. ALTDDIO_IN IP Core Signals
1.8. ALTDDIO_OUT IP Core Signals
1.9. ALTDDIO_BIDIR IP Core Signals
1.10. Verilog HDL Prototype
1.11. VHDL Component Declaration
1.12. VHDL LIBRARY-USE Declaration
1.13. Double Data Rate I/O (ALTDDIO_IN, ALTDDIO_OUT, and ALTDDIO_BIDIR) IP Cores User Guide Archives
1.14. Document Revision History
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1.2.2. QDR SRAM and QDRII SRAM Memory Interfaces
The QDR and QDRII SRAM standard is defined jointly by Cypress Semiconductor Corporation, Integrated Device Technology, Inc., and Micron Technology, Inc.
QDR and QDRII SRAMs have separate DDR read and write ports that pass data concurrently. The combination of concurrent transactions and DDR signaling allows data to be passed four times faster than by conventional SRAMs. The I/O standards used for QDR SRAM devices are 1.5-V HSTL class I and II. QDRII SRAMs use both 1.5-V and 1.8-V HSTL class I.