upsilon/firmware/rtl/autoapproach/bram_interface.v

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module bram_interface #(
parameter WORD_WID = 24,
parameter WORD_AMNT_WID = 11,
/* This is the last INDEX, not the LENGTH of the word array. */
parameter [WORD_AMNT_WID-1:0] WORD_AMNT = 2047,
parameter RAM_WID = 32,
parameter RAM_WORD_WID = 16,
parameter RAM_WORD_INCR = 2
) (
input clk,
/* autoapproach interface */
output reg [WORD_WID-1:0] word,
input word_next,
output reg word_last,
output reg word_ok,
input word_rst,
/* User interface */
input refresh_start,
input [RAM_WID-1:0] start_addr,
output reg refresh_finished,
/* RAM interface */
output reg [RAM_WID-1:0] ram_dma_addr,
input [RAM_WORD_WID-1:0] ram_word,
output reg ram_read,
input ram_valid
);
initial word = 0;
initial word_last = 0;
initial word_ok = 0;
initial refresh_finished = 0;
initial ram_dma_addr = 0;
initial ram_read = 0;
reg [WORD_WID-1:0] backing_buffer [WORD_AMNT:0];
localparam WAIT_ON_REFRESH = 0;
localparam READ_LOW_WORD = 1;
localparam READ_HIGH_WORD = 2;
localparam WAIT_ON_REFRESH_DEASSERT = 3;
reg [1:0] refresh_state = 0;
reg [WORD_AMNT_WID-1:0] word_cntr_refresh = 0;
always @ (posedge clk) case (refresh_state)
WAIT_ON_REFRESH: if (refresh_start) begin
ram_dma_addr <= start_addr;
refresh_state <= READ_LOW_WORD;
word_cntr_refresh <= 0;
end
READ_LOW_WORD: if (!ram_read) begin
ram_read <= 1;
end else if (ram_valid) begin
refresh_state <= READ_HIGH_WORD;
ram_dma_addr <= ram_dma_addr + RAM_WORD_INCR;
ram_read <= 0;
backing_buffer[word_cntr_refresh][RAM_WORD_WID-1:0] <= ram_word;
end
READ_HIGH_WORD: if (!ram_read) begin
ram_read <= 1;
end else if (ram_valid) begin
ram_dma_addr <= ram_dma_addr + RAM_WORD_INCR;
ram_read <= 0;
word_cntr_refresh <= word_cntr_refresh + 1;
backing_buffer[word_cntr_refresh][WORD_WID-1:RAM_WORD_WID] <= ram_word[WORD_WID-RAM_WORD_WID-1:0];
if (word_cntr_refresh == WORD_AMNT)
refresh_state <= WAIT_ON_REFRESH_DEASSERT;
else
refresh_state <= READ_LOW_WORD;
end
WAIT_ON_REFRESH_DEASSERT: begin
if (!refresh_start) begin
refresh_finished <= 0;
refresh_state <= WAIT_ON_REFRESH;
end else begin
refresh_finished <= 1;
end
end
endcase
reg [WORD_AMNT_WID-1:0] auto_cntr = 0;
always @ (posedge clk) if (word_rst) begin
auto_cntr <= 0;
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word_ok <= 0;
word_last <= 0;
word <= 0;
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end else if (word_next && !word_ok) begin
if (refresh_state == WAIT_ON_REFRESH) begin
word <= backing_buffer[auto_cntr];
word_ok <= 1;
if (auto_cntr == WORD_AMNT) begin
auto_cntr <= 0;
word_last <= 1;
end else begin
auto_cntr <= auto_cntr + 1;
word_last <= 0;
end
end
end else if (!word_next && word_ok) begin
word_ok <= 0;
end
endmodule