ARM FPGA Extended Memory Interface

Connect a ARM Microcontroller to a FPGA using its Extended Memory Interface (EMI)

For a transfer of data to the FPGA, the direction of the bidirectional buffers in the PIO must be set to output. The software algorithm that transfers data to the FPGA is as follows:

PIO_DATA = ADDRESS; // Pass the address to write

PIO_CTROL = START | WR; // Send start of address cycle

PIO_CTROL = CLEAR; // Clear PIO ctrl, this ends the address cycle

PIO_DATA = DATA; // Set data to transfer

PIO_CTROL = START; // Data is ready in PIO

PIO_CTROL = CLEAR; // This ends the data cycle

Reading from the FPGA is similar. Again, the direction of the buffer on the PIO must first be set to output and then change directions to input to read the data from the FPGA, the following code is executed:

PIO_DATA = ADDRESS; // Set the address to read

PIO_CTROL = START | RD; // Send start of address cycle

PIO_CTROL = CLEAR; // Clear PIO ctrl, this ends the address cycle

PIO_DATA_DIR = INPUT; // Set PIO-Data direction as input to receive the data

DELAY(WAIT_FOR_FPGA); // wait for the FPGA to send the data

DATA_FROM_FPGA = PIO_DATA; // Read data from FPGA