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module spiflash (
input spi_cs,
output reg spi_miso,
input spi_mosi,
input spi_sclk
);
localparam verbose = 1;
reg [7:0] buffer;
integer bitcount = 0;
integer bytecount = 0;
reg [7:0] spi_cmd;
reg [23:0] spi_addr;
reg [7:0] spi_in;
reg [7:0] spi_out;
reg spi_io_vld;
reg powered_up = 0;
reg in_xfer = 0;
// 16 MB (128Mb) Flash
reg [7:0] memory [0:16*1024*1024-1];
initial begin
$readmemh("firmware.hex", memory);
end
task spi_action;
begin
if (verbose) begin
if (bytecount == 1)
$write("<SPI>");
$write("<SPI:%02x", buffer);
spi_in = buffer;
end
if (bytecount == 1) begin
spi_cmd = buffer;
if (spi_cmd == 8'hAB)
powered_up = 1;
if (spi_cmd == 8'hB9)
powered_up = 0;
end
if (powered_up && spi_cmd == 'h03) begin
if (bytecount == 2)
spi_addr[23:16] = buffer;
if (bytecount == 3)
spi_addr[15:8] = buffer;
if (bytecount == 4)
spi_addr[7:0] = buffer;
if (bytecount >= 4) begin
buffer = memory[spi_addr];
spi_addr = spi_addr + 1;
end
end
if (verbose) begin
$write(":%02x>", buffer);
spi_out = buffer;
spi_io_vld = 1;
$fflush;
end
end
endtask
always @(spi_cs) begin
if (spi_cs) begin
if (verbose && in_xfer) begin
$display("");
$fflush;
end
buffer = 0;
in_xfer = 0;
bitcount = 0;
bytecount = 0;
spi_miso = 0;
end
end
always @(spi_cs, spi_sclk) begin
spi_io_vld = 0;
if (!spi_cs && !spi_sclk) begin
spi_miso = buffer[7];
end
end
always @(posedge spi_sclk) begin
if (!spi_cs) begin
buffer = {buffer, spi_mosi};
bitcount = bitcount + 1;
if (bitcount == 8) begin
in_xfer = 1;
bitcount = 0;
bytecount = bytecount + 1;
spi_action;
end
end
end
endmodule
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