zynq Nand flash，QSPI，EMMC接口

Static Memory Controller (SMC) Interface:Only one SMC memory interface can be used in a design. The SMC controller consumes many of the MIO pins and neither of the SMC memory interfaces can be routed to the EMIO.
For example, if an 8-bit NAND Flash is implemented, then Quad-SPI, is not available and the test port is limited to 8-bits. If a 16-bit NAND Flash is implemented, then additional pins are consumed.Ethernet 0 is not available. The SRAM/NOR interface consumes up to 70% of the MIO pins,

eliminating Ethernet and USB 0.

flash有三种方式：

1.客户直接选一颗稍大容量QSPI，程序通过QSPI加载；

2.选用Nand Flash加载程序，但是客户可能会担心Nand Flash有坏块不好管理；

3.选用小QSPI Flash，镜像文件跟用户数据存储在EMMC存储器，eMMC存贮器走SDIO2.0协议，最大支持32G bit；1

DDR3 SDRAM：

1.DDR3 SDRAM 最大支持8G bit