RAM的初始化

RAM可以通过以下方式初始化：
1，在HDL源代码中指定RAM初始内容；
2，在外部数据文件中指定RAM初始内容。
Verilog Coding Example：

1，所有可寻址的words都初始化为相同的值

reg [DATA_WIDTH-1:0] ram [DEPTH-1:0]; integer i; initial for (i=0; i<DEPTH; i=i+1) ram[i] = 0; end 

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2,在外部数据文件中指定RAM初始内容

使用HDL源代码中的文件读取函数从外部数据文件加载RAM初始内容。
以下外部数据文件使用二进制值初始化8x32位RAM：

00001110110000011001111011000110 00101011001011010101001000100011 01110100010100011000011100001111 01000001010000100101001110010100 00001001101001111111101000101011 00101101001011111110101010100111 11101111000100111000111101101101 10001111010010011001000011101111 ................................ 

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Code Example (Verilog):

reg [31:0] ram [0:63]; 
initial begin 
$readmemb(“rams_20c.data”, ram, 0, 63); 
end 

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3 Initializing Block RAM (Verilog)

// Initializing Block RAM (Single-Port Block RAM)  // File: rams_sp_rom  module rams_sp_rom (clk, we, addr, di, dout); input clk; input we; input [5:0] addr; input [19:0] di; output [19:0] dout; reg [19:0] ram [63:0]; reg [19:0] dout; initial 
begin 
ram[63] = 20'h0200A; ram[62] = 20'h00300; ram[61] = 20'h08101; ram[60] = 20'h04000; ram[59] = 20'h08601; ram[58] = 20'h0233A; ram[57] = 20'h00300; ram[56] = 20'h08602; ram[55] = 20'h02310; ram[54] = 20'h0203B; ram[53] = 20'h08300; ram[52] = 20'h04002; ram[51] = 20'h08201; ram[50] = 20'h00500; ram[49] = 20'h04001; ram[48] = 20'h02500; ram[47] = 20'h00340; ram[46] = 20'h00241; ram[45] = 20'h04002; ram[44] = 20'h08300; ram[43] = 20'h08201; ram[42] = 20'h00500; ram[41] = 20'h08101; ram[40] = 20'h00602; ram[39] = 20'h04003; ram[38] = 20'h0241E; ram[37] = 20'h00301; ram[36] = 20'h00102; ram[35] = 20'h02122; ram[34] = 20'h02021; ram[33] = 20'h00301; ram[32] = 20'h00102; ram[31] = 20'h02222; ram[30] = 20'h04001; ram[29] = 20'h00342; ram[28] = 20'h0232B; ram[27] = 20'h00900; ram[26] = 20'h00302; ram[25] = 20'h00102; ram[24] = 20'h04002; ram[23] = 20'h00900; ram[22] = 20'h08201; ram[21] = 20'h02023; ram[20] = 20'h00303; ram[19] = 20'h02433; ram[18] = 20'h00301; ram[17] = 20'h04004; ram[16] = 20'h00301; ram[15] = 20'h00102; ram[14] = 20'h02137; ram[13] = 20'h02036; ram[12] = 20'h00301; ram[11] = 20'h00102; ram[10] = 20'h02237; ram[9] = 20'h04004; ram[8] = 20'h00304; ram[7] = 20'h04040; ram[6] = 20'h02500; ram[5] = 20'h02500; ram[4] = 20'h02500; ram[3] = 20'h0030D; ram[2] = 20'h02341; ram[1] = 20'h08201; ram[0] = 20'h0400D; end 
always @(posedge clk) begin if (we) ram[addr] <= di; dout <= ram[addr]; end 
endmodule 

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4,从外部数据文件初始化块RAM(Verilog)

// Initializing Block RAM from external data file  // Binary data  // File: rams_init_file.v  module rams_init_file (clk, we, addr, din, dout); input clk; input we; input [5:0] addr; input [31:0] din; output [31:0] dout; reg [31:0] ram [0:63]; reg [31:0] dout; initial begin 
$readmemb("rams_init_file.data",ram); end 
always @(posedge clk) begin if (we) ram[addr] <= din; dout <= ram[addr]; end 
endmodule 

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用于初始化RAM的外部文件需要以位向量形式。整数或十六进制格式的外部文件将无法工作。