External Memory Interface Handbook Volume 2: Design Guidelines

ID 683385
Date 5/08/2017
Document Table of Contents

1.4.4. Pin-out Rule Exceptions for QDR II and QDR II+ SRAM Burst-length-of-two Interfaces

If you are using the QDR II and QDR II+ SRAM burst-length-of-two devices, you may want to place the address pins in a DQS group to minimize skew, because these pins are now double data rate too.

The address pins typically do not exceed 22 bits, so you may use one ×18 DQS groups or two ×9 DQS groups on the same side of the device, if not the same I/O bank. In Arria V GZ, Stratix III, Stratix IV, and Stratix V devices, one ×18 group typically has 22 DQ bits and 2 pins for DQS/DQSn pins, while one ×9 group typically has 10 DQ bits with 2 pins for DQS/DQSn pins. Using ×4 DQS groups should be a last resort.

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