2 // Wishbone module for spi communications with an SD Card
3 // The programming interface is simple --
4 // Write the desired clock divider to address 1 (should be 1 or higher)
5 // Status is in address 0. A 1 indicates the last transaction is done and it is safe to
7 // Writing a byte to address 2 sends that byte over SPI. When it is done,
8 // status (addr 0) goes high again, and the received byte can be read from address 3.
25 output reg [7:0] wb_dat_o,
28 localparam ADDR_STATUS = 0;
29 localparam ADDR_CLKDIV = 1;
30 localparam ADDR_WRITE = 2;
31 localparam ADDR_READ = 3;
33 wire [7:0] status, rcv_dat;
39 assign sd_csn = ~cs_reg; // FIXME
43 else ack_d1 <= wb_ack_o;
46 if(rst) wb_ack_o <= 0;
47 else wb_ack_o <= wb_cyc_i & wb_stb_i & ~ack_d1;
51 ADDR_STATUS : wb_dat_o <= {7'd0,ready};
52 ADDR_CLKDIV : wb_dat_o <= clkdiv;
53 ADDR_READ : wb_dat_o <= rcv_dat;
54 default : wb_dat_o <= 0;
55 endcase // case(wb_adr_i)
63 else if(wb_we_i & wb_stb_i & wb_cyc_i & wb_ack_o)
65 ADDR_STATUS : cs_reg <= wb_dat_i;
66 ADDR_CLKDIV : clkdiv <= wb_dat_i;
67 endcase // case(wb_adr_i)
69 wire go = wb_we_i & wb_stb_i & wb_cyc_i & wb_ack_o & (wb_adr_i == ADDR_WRITE);
71 sd_spi sd_spi(.clk(clk),.rst(rst),
72 .sd_clk(sd_clk),.sd_mosi(sd_mosi),.sd_miso(sd_miso),
73 .clk_div(clkdiv),.send_dat(wb_dat_i),.rcv_dat(rcv_dat),
74 .go(go),.ready(ready) );
76 endmodule // sd_spi_wb