SD card support on Series 2 FPGA Boards

By introduction of Series 2 FPGA Boards the microSD socket used on Series 1 FPGA Boards has been replaced by fixed SPI Flash. Nevertheless, SD-Card support can be easily be re-enabled by adding an (micro)SD card socket to the application circuit and routing the signals through FPGA. This is explained best by an example:

A SD card is connected to an USB-FPGA Module 2.01 as follows

The HDL code for routing the signals looks like:

# ...
NET "pa2"	LOC = "B10" | IOSTANDARD = LVCMOS33 ;		# PA2
NET "pc1"	LOC = "N12" | IOSTANDARD = LVCMOS33 ;		# PC1/GPIFADR1
NET "pc2"	LOC = "P12" | IOSTANDARD = LVCMOS33 ;		# PC2/GPIFADR2
NET "pc3"	LOC = "N5" | IOSTANDARD = LVCMOS33 ;		# PC3/GPIFADR3
 
NET "b13"	LOC = "K15" | IOSTANDARD = LVCMOS33 ;	
NET "b14"	LOC = "J13" | IOSTANDARD = LVCMOS33 ;
NET "b18"	LOC = "J14" | IOSTANDARD = LVCMOS33 ;
NET "b19"	LOC = "H15" | IOSTANDARD = LVCMOS33 ;
 
# ...

(.ucf constraints file) and

// ...
 
module top (
 
        // ...
 
	input pc1,pc2,pc3, b19,
	output b13,b14,b18, pa2
    );
 
    // ...
 
    assign b13 = pc1;
    assign b14 = pc2;
    assign b18 = pc3;
    assign pa2 = b19;
 
    // ...
 
endmodule

(verilog HDL file).

In order to enable firmware support the following lines have to be inserted between #include[ztex-conf.h] and #include[ztex.h]

ENABLE_FLASH2;            // enables SD support as secondary Flash
#define[MMC_PORT][C]      // Port for input signals, valid values: A..D
#define[MMC__PORT_DO][A]  // Port for output signals (valid values: A..D,
                          // can be omitted if equal to input port)
#define[MMC_BIT_CS][1]    // Pin number for CS signal, i.e. PC1
#define[MMC_BIT_DI][2]    // Pin number for DI signal, i.e. PC2
#define[MMC_BIT_DO][2]    // Pin number for DO signal, i.e. PA2
#define[MMC_BIT_CLK][3]   // Pin number for CLK signal, i.e. PC3

The SD card now can be accessed using the functions flash2_read_init, flash2_read, flash2_read_finish