diff options
Diffstat (limited to 'fpga/usrp2/control_lib/ram_loader.v')
| -rw-r--r-- | fpga/usrp2/control_lib/ram_loader.v | 261 |
1 files changed, 261 insertions, 0 deletions
diff --git a/fpga/usrp2/control_lib/ram_loader.v b/fpga/usrp2/control_lib/ram_loader.v new file mode 100644 index 000000000..c53ea7aa7 --- /dev/null +++ b/fpga/usrp2/control_lib/ram_loader.v @@ -0,0 +1,261 @@ +module ram_loader + #(parameter AWIDTH=16, RAM_SIZE=16384) + ( + // Wishbone I/F and clock domain + input wb_clk, + input dsp_clk, + input ram_loader_rst, + output wire [31:0] wb_dat, + output wire [AWIDTH-1:0] wb_adr, + output wb_stb, + output reg [3:0] wb_sel, + output wb_we, + output reg ram_loader_done, + // CPLD signals and clock domain + input cpld_clk, + input cpld_din, + output reg cpld_start, + output reg cpld_mode, + output reg cpld_done, + input cpld_detached + ); + + localparam S0 = 0; + localparam S1 = 1; + localparam S2 = 2; + localparam S3 = 3; + localparam S4 = 4; + localparam S5 = 5; + localparam S6 = 6; + localparam RESET = 7; + + localparam WB_IDLE = 0; + localparam WB_WRITE = 1; + + + reg [AWIDTH+2:0] count; // 3 LSB's count bits in, the MSB's generate the Wishbone address + reg [6:0] shift_reg; + reg [7:0] data_reg; + reg sampled_clk; + reg sampled_clk_meta; + reg sampled_din; + reg inc_count; + reg load_data_reg; + reg shift; + reg wb_state, wb_next_state; + reg [2:0] state, next_state; + + // + // CPLD clock doesn't free run and is approximately 12.5MHz. + // Use 50MHz Wishbone clock to sample it as a signal and avoid having + // an extra clock domain for no reason. + // + + always @(posedge dsp_clk or posedge ram_loader_rst) + if (ram_loader_rst) + begin + sampled_clk_meta <= 1'b0; + sampled_clk <= 1'b0; + sampled_din <= 1'b0; + count <= 'h7FFF8; // Initialize so that address will be 0 when first byte fully received. + data_reg <= 0; + shift_reg <= 0; + end + else + begin + sampled_clk_meta <= cpld_clk; + sampled_clk <= sampled_clk_meta; + sampled_din <= cpld_din; + if (inc_count) + count <= count + 1'b1; + if (load_data_reg) + data_reg <= {shift_reg,sampled_din}; + if (shift) + shift_reg <= {shift_reg[5:0],sampled_din}; + end // else: !if(ram_loader_rst) + + + always @(posedge dsp_clk or posedge ram_loader_rst) + if (ram_loader_rst) + state <= RESET; + else + state <= next_state; + + + always @* + begin + // Defaults + next_state = state; + cpld_start = 1'b0; + shift = 1'b0; + inc_count = 0; + load_data_reg = 1'b0; + ram_loader_done = 1'b0; + cpld_mode = 1'b0; + cpld_done = 1'b1; + + + + case (state) //synthesis parallel_case full_case + // After reset wait until CPLD indicates its detached. + RESET: begin + if (cpld_detached) + next_state = S0; + else + next_state = RESET; + end + + // Assert cpld_start to signal the CPLD its to start sending serial clock and data. + // Assume cpld_clk is low as we transition into search for first rising edge + S0: begin + cpld_start = 1'b1; + cpld_done = 1'b0; + if (~cpld_detached) + next_state = S2; + else + next_state = S0; + end + + // + S1: begin + cpld_start = 1'b1; + cpld_done = 1'b0; + if (sampled_clk) + begin + // Found rising edge on cpld_clk. + if (count[2:0] == 3'b111) + // Its the last bit of a byte, send it out to the Wishbone bus. + begin + load_data_reg = 1'b1; + inc_count = 1'b1; + end + else + // Shift databit into LSB of shift register and increment count + begin + shift = 1'b1; + inc_count = 1'b1; + end // else: !if(count[2:0] == 3'b111) + next_state = S2; + end // if (sampled_clk) + else + next_state = S1; + end // case: S1 + + // + S2: begin + cpld_start = 1'b1; + cpld_done = 1'b0; + if (~sampled_clk) + // Found negative edge of clock + if (count[AWIDTH+2:3] == RAM_SIZE-1) // NOTE need to change this constant + // All firmware now downloaded + next_state = S3; + else + next_state = S1; + else + next_state = S2; + end // case: S2 + + // Now that terminal count is reached and all firmware is downloaded signal CPLD that download is done + // and that mode is now SPI mode. + S3: begin + if (sampled_clk) + begin + cpld_mode = 1'b1; + cpld_done = 1'b1; + next_state = S4; + end + else + next_state = S3; + end + + // Search for negedge of cpld_clk whilst keeping done sequence asserted. + // Keep done assserted + S4: begin + cpld_mode = 1'b1; + cpld_done = 1'b1; + if (~sampled_clk) + next_state = S5; + else + next_state = S4; + end + + // Search for posedge of cpld_clk whilst keeping done sequence asserted. + S5: begin + cpld_mode = 1'b1; + cpld_done = 1'b1; + if (sampled_clk) + next_state = S6; + else + next_state = S5; + end + + // Stay in this state until reset/power down + S6: begin + ram_loader_done = 1'b1; + cpld_done = 1'b1; + cpld_mode = 1'b1; + next_state = S6; + end + + endcase // case(state) + end + + always @(posedge dsp_clk or posedge ram_loader_rst) + if (ram_loader_rst) + wb_state <= WB_IDLE; + else + wb_state <= wb_next_state; + + reg do_write; + wire empty, full; + + always @* + begin + wb_next_state = wb_state; + do_write = 1'b0; + + case (wb_state) //synthesis full_case parallel_case + // + WB_IDLE: begin + if (load_data_reg) + // Data reg will load ready to write wishbone @ next clock edge + wb_next_state = WB_WRITE; + else + wb_next_state = WB_IDLE; + end + + // Drive address and data onto wishbone. + WB_WRITE: begin + do_write = 1'b1; + if (~full) + wb_next_state = WB_IDLE; + else + wb_next_state = WB_WRITE; + end + + endcase // case(wb_state) + end // always @ * + + wire [1:0] count_out; + wire [7:0] data_out; + + fifo_xlnx_16x40_2clk crossclk + (.rst(ram_loader_rst), + .wr_clk(dsp_clk), .din({count[4:3],count[AWIDTH+2:3],data_reg}), .wr_en(do_write), .full(full), + .rd_clk(wb_clk), .dout({count_out,wb_adr,data_out}), .rd_en(~empty), .empty(empty)); + + assign wb_dat = {4{data_out}}; + + always @* + case(count_out[1:0]) //synthesis parallel_case full_case + 2'b00 : wb_sel = 4'b1000; + 2'b01 : wb_sel = 4'b0100; + 2'b10 : wb_sel = 4'b0010; + 2'b11 : wb_sel = 4'b0001; + endcase + + assign wb_we = ~empty; + assign wb_stb = ~empty; + +endmodule // ram_loader |