I am designing a new board which uses the NXP LPC4330 (Cortex M4 microcontroller) with a XESS Xula2 FPGA development board. In this design, the Xula 2 has limited I/O pins since it is designed to fit into a DIP-40 form factor. The primary form of communication between the micro and the FPGA is through SPI.
I would like the bus to be fairly high speed, on the order of 80 to 100 Mbps. It might be enough to run a single SPI port at 80 MHz, but since the main clock on the FPGA is only running at 120 MHz (and it drives the SPI interface), I'm not sure that the SPI would work at such a high data rate. The LPC4330 has multiple SPI ports, and one idea I have is to use 2 SPI ports so that each can run at a slower bit rate. There is plenty of room on the Spartan 6 FPGA, but I do not have the I/O pins on the development board to have 2 sets of all 3 of MOSI/MISO/SCK (plus a single CS).
Therefore, I am wondering if it is possible to synchronize the ports on the LPC such that they share a SPI clock. The fast communication only has to happen in a single direction, so I would only need to double up the MISO pin (the micro needs to read quickly from the FPGA, not vice versa). There doesn't appear to be a special mode to synchronize the SPI ports, but I assume that they would be on the same clock domain due to the clocking architecture of the micro.
I realize there is also a multi-port SPIFI (spi-flash memory interface) on the NXP. Has anyone had an experience creating a block on the FPGA which basically emulates a SPI flash?
So my questions are a) do you think this will work? and b) is there a better way to do this?