// OpenRAM SRAM model
// Words: 512
// Word size: 32
// Write size: 8

module sky130_sram_2kbyte_1rw1r_32x512_8(
    `ifdef USE_POWER_PINS
        vccd1,
        vssd1,
    `endif
    // Port 0: RW
        clk0,csb0,web0,wmask0,addr0,din0,dout0,
    // Port 1: R
        clk1,csb1,addr1,dout1
      );
    
      parameter NUM_WMASKS = 4 ;
      parameter DATA_WIDTH = 32 ;
      parameter ADDR_WIDTH = 9 ;
      parameter RAM_DEPTH = 1 << ADDR_WIDTH;
      // FIXME: This delay is arbitrary.
      parameter DELAY = 3 ;
      parameter VERBOSE = 1 ; //Set to 0 to only display warnings
      parameter T_HOLD = 1 ; //Delay to hold dout value after posedge. Value is arbitrary
    
    `ifdef USE_POWER_PINS
        inout vccd1;
        inout vssd1;
    `endif
      input  clk0; // clock
      input   csb0; // active low chip select
      input  web0; // active low write control
      input [NUM_WMASKS-1:0]   wmask0; // write mask
      input [ADDR_WIDTH-1:0]  addr0;
      input [DATA_WIDTH-1:0]  din0;
      output [DATA_WIDTH-1:0] dout0;
      input  clk1; // clock
      input   csb1; // active low chip select
      input [ADDR_WIDTH-1:0]  addr1;
      output [DATA_WIDTH-1:0] dout1;
    
      reg  csb0_reg;
      reg  web0_reg;
      reg [NUM_WMASKS-1:0]   wmask0_reg;
      reg [ADDR_WIDTH-1:0]  addr0_reg;
      reg [DATA_WIDTH-1:0]  din0_reg;
      reg [DATA_WIDTH-1:0]  dout0;
    
      // All inputs are registers
      always @(posedge clk0)
      begin
        csb0_reg = csb0;
        web0_reg = web0;
        wmask0_reg = wmask0;
        addr0_reg = addr0;
        din0_reg = din0;
        #(T_HOLD) dout0 <= 32'bx;
        if ( !csb0_reg && web0_reg && VERBOSE ) 
          $display($time," Reading %m addr0=%b dout0=%b",addr0_reg,mem[addr0_reg]);
        if ( !csb0_reg && !web0_reg && VERBOSE )
          $display($time," Writing %m addr0=%b din0=%b wmask0=%b",addr0_reg,din0_reg,wmask0_reg);
      end
    
      reg  csb1_reg;
      reg [ADDR_WIDTH-1:0]  addr1_reg;
      reg [DATA_WIDTH-1:0]  dout1;
    
      // All inputs are registers
      always @(posedge clk1)
      begin
        csb1_reg = csb1;
        addr1_reg = addr1;
        if (!csb0 && !web0 && !csb1 && (addr0 == addr1))
             $display($time," WARNING: Writing and reading addr0=%b and addr1=%b simultaneously!",addr0,addr1);
        #(T_HOLD) dout1 <= 32'bx;
        if ( !csb1_reg && VERBOSE ) 
          $display($time," Reading %m addr1=%b dout1=%b",addr1_reg,mem[addr1_reg]);
      end
    
    reg [DATA_WIDTH-1:0]    mem [0:RAM_DEPTH-1];
    
      // Memory Write Block Port 0
      // Write Operation : When web0 = 0, csb0 = 0
      always @ (negedge clk0)
      begin : MEM_WRITE0
        if ( !csb0_reg && !web0_reg ) begin
            if (wmask0_reg[0])
                    mem[addr0_reg][7:0] = din0_reg[7:0];
            if (wmask0_reg[1])
                    mem[addr0_reg][15:8] = din0_reg[15:8];
            if (wmask0_reg[2])
                    mem[addr0_reg][23:16] = din0_reg[23:16];
            if (wmask0_reg[3])
                    mem[addr0_reg][31:24] = din0_reg[31:24];
        end
      end
    
      // Memory Read Block Port 0
      // Read Operation : When web0 = 1, csb0 = 0
      always @ (negedge clk0)
      begin : MEM_READ0
        if (!csb0_reg && web0_reg)
           dout0 <= #(DELAY) mem[addr0_reg];
      end
    
      // Memory Read Block Port 1
      // Read Operation : When web1 = 1, csb1 = 0
      always @ (negedge clk1)
      begin : MEM_READ1
        if (!csb1_reg)
           dout1 <= #(DELAY) mem[addr1_reg];
      end

      initial begin
        $display("Reading Memory");
        $readmemh("imem.hex", mem);
      end
    
    endmodule