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module extram_wb
#(parameter PAGE_SIZE = 10,
parameter ADDR_WIDTH = 16)
(input clk, input rst,
input wb_clk, input wb_rst,
input cyc_i, input stb_i,
input [ADDR_WIDTH-1:0] adr_i,
input we_i,
input [31:0] dat_i,
output reg [31:0] dat_o,
output reg ack_o,
inout [17:0] RAM_D,
output [PAGE_SIZE-2:0] RAM_A,
output RAM_CE1n, output RAM_CENn,
output RAM_CLK, output RAM_WEn,
output RAM_OEn, output RAM_LDn );
wire read_acc = stb_i & cyc_i & ~we_i;
wire write_acc = stb_i & cyc_i & we_i;
wire acc = stb_i & cyc_i;
assign RAM_CLK = ~wb_clk; // 50 MHz for now, eventually should be 200 MHz
assign RAM_LDn = 0; // No burst for now
assign RAM_CENn = 0; // Use CE1n as our main CE
reg [PAGE_SIZE-2:1] RAM_addr_reg;
always @(posedge wb_clk)
if(acc)
RAM_addr_reg[PAGE_SIZE-2:1] <= adr_i[PAGE_SIZE-1:2];
assign RAM_A[PAGE_SIZE-2:1] = RAM_addr_reg;
reg [31:0] ram_out;
always @(posedge wb_clk)
if(write_acc)
ram_out <= dat_i;
// RAM access state machine
localparam RAM_idle = 0;
localparam RAM_read_1 = 1;
localparam RAM_read_2 = 2;
localparam RAM_read_3 = 3;
localparam RAM_read_4 = 4;
localparam RAM_write_1 = 6;
localparam RAM_write_2 = 7;
localparam RAM_write_3 = 8;
localparam RAM_write_4 = 9;
reg myOE = 0;
reg RAM_OE = 0;
reg RAM_WE = 0;
reg RAM_EN = 0;
reg RAM_A0_reg;
reg [3:0] RAM_state;
always @(posedge wb_clk)
if(wb_rst)
begin
RAM_state <= RAM_idle;
myOE <= 0; RAM_OE <= 0; RAM_WE <= 0; RAM_EN <= 0; RAM_A0_reg <= 0;
end
else
case(RAM_state)
RAM_idle :
if(read_acc & ~ack_o)
begin
RAM_state <= RAM_read_1;
myOE <= 0; RAM_OE <= 0; RAM_WE <= 0; RAM_EN <= 1; RAM_A0_reg <= 0;
end
else if(write_acc & ~ack_o)
begin
RAM_state <= RAM_write_1;
myOE <= 0; RAM_OE <= 0; RAM_WE <= 1; RAM_EN <= 1; RAM_A0_reg <= 0;
end
else
begin
myOE <= 0; RAM_OE <= 0; RAM_WE <= 0; RAM_EN <= 0; RAM_A0_reg <= 0;
end
RAM_read_1 :
begin
RAM_state <= RAM_read_2;
myOE <= 0; RAM_OE <= 0; RAM_WE <= 0; RAM_EN <= 1; RAM_A0_reg <= 1;
end
RAM_read_2 :
begin
RAM_state <= RAM_read_3;
myOE <= 0; RAM_OE <= 1; RAM_WE <= 0; RAM_EN <= 0; RAM_A0_reg <= 0;
end
RAM_read_3 :
begin
RAM_state <= RAM_read_4;
myOE <= 0; RAM_OE <= 1; RAM_WE <= 0; RAM_EN <= 0; RAM_A0_reg <= 0;
end
RAM_read_4 :
begin
RAM_state <= RAM_idle;
myOE <= 0; RAM_OE <= 0; RAM_WE <= 0; RAM_EN <= 0; RAM_A0_reg <= 0;
end
RAM_write_1 :
begin
RAM_state <= RAM_write_2;
myOE <= 1; RAM_OE <= 0; RAM_WE <= 1; RAM_EN <= 1; RAM_A0_reg <= 1;
end
RAM_write_2 :
begin
RAM_state <= RAM_write_3;
myOE <= 1; RAM_OE <= 0; RAM_WE <= 0; RAM_EN <= 0; RAM_A0_reg <= 0;
end
RAM_write_3 :
begin
RAM_state <= RAM_write_4;
myOE <= 1; RAM_OE <= 0; RAM_WE <= 0; RAM_EN <= 0; RAM_A0_reg <= 0;
end
RAM_write_4 :
begin
RAM_state <= RAM_idle;
myOE <= 0; RAM_OE <= 0; RAM_WE <= 0; RAM_EN <= 0; RAM_A0_reg <= 0;
end
default : RAM_state <= RAM_idle;
endcase // case(RAM_state)
assign RAM_A[0] = RAM_A0_reg;
assign RAM_WEn = ~RAM_WE; // ((RAM_state==RAM_write_1)||(RAM_state==RAM_write_2));
assign RAM_OEn = ~RAM_OE;
assign RAM_CE1n = ~RAM_EN; // Active low (RAM_state != RAM_idle);
assign RAM_D[17:16] = 2'bzz;
assign RAM_D[15:0] = myOE ? ((RAM_state==RAM_write_2)?ram_out[15:0]:ram_out[31:16])
: 16'bzzzz_zzzz_zzzz_zzzz;
always @(posedge wb_clk)
if(RAM_state == RAM_read_3)
dat_o[15:0] <= RAM_D[15:0];
else
dat_o[31:16] <= RAM_D[15:0];
always @(posedge wb_clk)
if(wb_rst)
ack_o <= 0;
else if((RAM_state == RAM_write_4)||(RAM_state == RAM_read_4))
ack_o <= 1;
else
ack_o <= 0;
endmodule // extram_wb
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