PL 读写DDR

PL是怎样访问DDR的?

zynq-7000的地址映射,PL作为主设备访问ddr时所用的地址是0x40000000-0x7FFFFFFF;

所以在搭建环境的时候要注意pl所给的地址为0x40000000-0x7FFFFFFF才能访问到PS的DDR。

另外值得注意的是Dcache的一致性问题,为了PL可以直接读到DDR的数据,在SDK初始化的时候用到的是mem test的模板的init_plateform()进行初始化,关掉Dcache,这样PL才能直接读到DDR,不然PS读的是缓存区的数据!!!这个是从网上查的资料。

软件初始化正确,PL设置的访问地址正确,才能访问到DDR!!!!!!!,注意是PL模块给PS的地址!!!!!!

### Zynq7045 PL DDR Read Write Implementation Tutorial In the context of Xilinx's Zynq-7045 SoC, interaction between the Processing System (PS) and Programmable Logic (PL), especially concerning access to shared DDR memory, is a critical aspect of system design. The PS can manage DDR3 through its own controllers while allowing the PL part to interact with this resource under certain configurations. For implementing read/write operations from/to DDR within the PL side: #### Configuration via Vivado HLS or IP Integrator To enable such functionality, one must configure an AXI GPIO interface or similar mechanism that allows communication over the High Performance (HP) ports connected directly to the DDR controller inside the PS[^1]. This setup facilitates direct memory access by providing address mapping into the global address space managed by the ARM cores in the PS section. #### Example Code for Reading/Writing Data Using C/C++ When developing software running on the PS side which interacts with hardware instantiated in the PL region, consider using APIs provided by Xilinx SDK as shown below: ```c // Initialize pointer to mapped address range corresponding to DDR segment accessible by PL. volatile unsigned int *pl_ddr_base_addr = XPAR_AXI_GPIO_0_BASEADDR; void write_to_pl_ddr(unsigned int offset, unsigned int value){ *(pl_ddr_base_addr + offset) = value; } unsigned int read_from_pl_ddr(unsigned int offset){ return *(pl_ddr_base_addr + offset); } ``` This code snippet demonstrates basic functions for writing data at specified offsets relative to the base address assigned during configuration and reading back values stored thereupon request. #### Interrupt-Based Approach vs Polling Methodology Initially, polling mechanisms may be employed where the processor continuously checks status registers until expected conditions are met indicating completion of tasks like writes being acknowledged or reads returning valid results. However, transitioning towards interrupt-driven models could enhance efficiency significantly once initial prototypes prove functional stability has been achieved. --related questions-- 1. What tools does Xilinx provide specifically tailored toward facilitating development involving both PS and PL components? 2. How do timing constraints affect performance when accessing off-chip memories like DDR3 through FPGA fabrics? 3. Can you elaborate more about best practices regarding power management strategies applicable here? 4. Are there any specific considerations needed when designing systems intended for real-time applications utilizing these features?
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