PCI or System Bus

I would like to hook up 1-4 FPGA devices to the NS9750. I am trying to decide whether I should memory map these FPGA “peripherals” to the system memory bus, or use the PCI port. Each FPGA(s) will have some finite amount of internal register and ram space that is memory-mapped, and will hook directly to external SRAM as large as perhaps 16Mbits. My application may require that the data contained in the FPGA SRAM is uploaded at once into the NS9750 and out through the Ethernet link. Otherwise, the link between the NS9750 and the FPGA(s) will be used only so the NS9750 can provision FPGA registers. On one hand, I thought that if I memory map the FPGA(s) onto the system memory bus, I don’t have to deal with PCI “bootup configuration” sequencing issues. On the other hand, perhaps using the PCI bus helps alleviates any performance issues of the NS9750 trying to access external RAM. Thanks for your thoughts.

Hi,Better memory map it. With PCI you have complicated timing requirements and you need to implement a configuration space. If you connect it directly to Memory bus you only have to be careful because the NS9750 has limited driver strength of 8mA. I know from experience that NS9750 works with a total Load of 6 Chips on address/data lines. Jochen