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The FPGAs referenced in these articles have complex dedicated I/O circuitries that are primarily designed to support external memory interfaces. The ALTMEMPHY megafunction is designed to support the most common memory standards, such as the DDR and DDR 2 SDRAM and QDR II+/QDR II SRAM (in a burst length of 4) interfaces. The ALTMEMPHY megafunction should be used whenever possible as it is beneficial to use the IP and timing closure methodologies used with these FPGAs, which enables users not to have to create this function manually as compared with using the ALTDLL and ALTDQ_DQS solution. However, the ALTMEMPHY megafunction does not support other external memory standards such as Mobile DDR, QDR II+/QDR II SRAM (in burst length of 2) or customized DDR and DDR 2 SDRAM external memory standards. For these scenarios, use the ALTDLL and ALTDQ_DQS megafunctions to access the FPGA architecture and build a custom external memory interface.

FPGAs referenced in this article have complex dedicated I/O circuitries that are primarily designed to support EMIF. The ALTMEMPHY megafunction is designed to support the most common memory standards, such as the DDR , DDR2 SDRAM, and QDR II+/QDR II SRAM (in a burst length of 4) interfaces. Other external memory standards such as Mobile DDR, QDR II+/QDR II SRAM (in burst length of 2), or customized DDR and DDR 2 SDRAM external memory standards are not supported. Instead, the ALTDLL and ALTDQ_DQS megafunctions are used to access the FPGA architecture and build a custom EMIF.