Double Data Rate I/O (ALTDDIO_IN, ALTDDIO_OUT, and ALTDDIO_BIDIR) IP Cores User Guide

ID 683148
Date 6/19/2017
Document Table of Contents

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.