MicroBlaze访问Zynq-7000的OCM

1. MicroBlaze AXI访问返回DECODE1C

在ZC702单板上，MicroBlaze通过IC/DC端口连接到PS S_AXI_GP0，MicroBlaze读取OCM，得到值DECODE1C。 DECODE1C is returned by the AXI Interconnect if it doesn't know how to route a requested AXI transaction. MicroBlaze改为通过DP端口连接到PS S_AXI_GP0，再读取OCM，正常。

2. OCM映射到高地址

Zynq-7000的OCM缺省部分映射到0地址，部分映射到0xFFFF0000。如果要把OCM全部映射到高地址，需要配置OCM_CFG寄存器。MicroBlaze不能访问OCM_CFG寄存器，一定要在A9里访问OCM_CFG寄存器。

    /*
    Register (slcr) OCM_CFG 
    Absolute Address 0xF8000910
    */
    xil_printf("Original OCM_CFG: 0x%08x\r\n", Xil_In32(0xF8000910) );
	Xil_Out32(SLCR_UNLOCK, SLCR_UNLOCK_VAL);
	Xil_Out32(0xF8000910, 0x1f);
	Xil_Out32(SLCR_LOCK, SLCR_LOCK_VAL);
    xil_printf("Updated OCM_CFG: 0x%08x\r\n", Xil_In32(0xF8000910) );

3. 参考文章

https://www.xilinx.com/support/answers/71416.html https://www.xilinx.com/video/soc/zynq-microblaze-iop-ocm-memory-resource-sharing.html