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ecc_block.v
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/* ECC check block (combinational block): validates the packet header info based on received ECC
* Gedeon Nyengele <nyengele@stanford.edu>
* 08 January 2018
*/
/*
* @param PH_in input packet header (input)
* @param PH_out possibly corrected PH without the ECC field (output)
* @param no_error signals whether the PH has no errors (output)
* @param corrected_error signals whether a single bit error was corrected (output)
* @param error signals whether the PH has an error that cannot be corrected (output)
*/
module ecc_block(PH_in, PH_out, no_error, corrected_error, error);
parameter PH_SIZE = 32;
parameter ECC_SIZE = 8;
input [(PH_SIZE-1):0] PH_in;
output reg [(PH_SIZE-ECC_SIZE-1):0] PH_out;
output reg no_error, corrected_error, error;
wire [(PH_SIZE-ECC_SIZE-1):0] data = PH_in[(PH_SIZE-ECC_SIZE-1):0];
reg [(ECC_SIZE-1):0] calc_ecc;
reg [(ECC_SIZE-1):0] syndrome;
always @(*) begin
// compute ECC
calc_ecc = {2'b00,
(^ {data[10], data[11], data[12], data[13], data[14], data[15], data[16], data[17], data[18], data[19], data[21], data[22], data[23]}),
(^ {data[4], data[5], data[6], data[7], data[8], data[9], data[16], data[17], data[18], data[19], data[20], data[22], data[23]}),
(^ {data[1], data[2], data[3], data[7], data[8], data[9], data[13], data[14], data[15], data[19], data[20], data[21], data[23]}),
(^ {data[0], data[2], data[3], data[5], data[6], data[9], data[11], data[12], data[15], data[18], data[20], data[21], data[22]}),
(^ {data[0], data[1], data[3], data[4], data[6], data[8], data[10], data[12], data[14], data[17], data[20], data[21], data[22], data[23]}),
(^ {data[0], data[1], data[2], data[4], data[5], data[7], data[10], data[11], data[13], data[16], data[20], data[21], data[22], data[23]})
};
// compute syndrome
syndrome = PH_in[(PH_SIZE-1):(PH_SIZE-ECC_SIZE)] ^ calc_ecc;
// correct data
case(syndrome)
8'h07 : begin {no_error, corrected_error, error} = 3'b010; PH_out = PH_in[(PH_SIZE-ECC_SIZE-1):0] ^ (1<<0); end
8'h0B : begin {no_error, corrected_error, error} = 3'b010; PH_out = PH_in[(PH_SIZE-ECC_SIZE-1):0] ^ (1<<1); end
8'h0D : begin {no_error, corrected_error, error} = 3'b010; PH_out = PH_in[(PH_SIZE-ECC_SIZE-1):0] ^ (1<<2); end
8'h0E : begin {no_error, corrected_error, error} = 3'b010; PH_out = PH_in[(PH_SIZE-ECC_SIZE-1):0] ^ (1<<3); end
8'h13 : begin {no_error, corrected_error, error} = 3'b010; PH_out = PH_in[(PH_SIZE-ECC_SIZE-1):0] ^ (1<<4); end
8'h15 : begin {no_error, corrected_error, error} = 3'b010; PH_out = PH_in[(PH_SIZE-ECC_SIZE-1):0] ^ (1<<5); end
8'h16 : begin {no_error, corrected_error, error} = 3'b010; PH_out = PH_in[(PH_SIZE-ECC_SIZE-1):0] ^ (1<<6); end
8'h19 : begin {no_error, corrected_error, error} = 3'b010; PH_out = PH_in[(PH_SIZE-ECC_SIZE-1):0] ^ (1<<7); end
8'h1A : begin {no_error, corrected_error, error} = 3'b010; PH_out = PH_in[(PH_SIZE-ECC_SIZE-1):0] ^ (1<<8); end
8'h1C : begin {no_error, corrected_error, error} = 3'b010; PH_out = PH_in[(PH_SIZE-ECC_SIZE-1):0] ^ (1<<9); end
8'h23 : begin {no_error, corrected_error, error} = 3'b010; PH_out = PH_in[(PH_SIZE-ECC_SIZE-1):0] ^ (1<<10); end
8'h25 : begin {no_error, corrected_error, error} = 3'b010; PH_out = PH_in[(PH_SIZE-ECC_SIZE-1):0] ^ (1<<11); end
8'h26 : begin {no_error, corrected_error, error} = 3'b010; PH_out = PH_in[(PH_SIZE-ECC_SIZE-1):0] ^ (1<<12); end
8'h29 : begin {no_error, corrected_error, error} = 3'b010; PH_out = PH_in[(PH_SIZE-ECC_SIZE-1):0] ^ (1<<13); end
8'h2A : begin {no_error, corrected_error, error} = 3'b010; PH_out = PH_in[(PH_SIZE-ECC_SIZE-1):0] ^ (1<<14); end
8'h2C : begin {no_error, corrected_error, error} = 3'b010; PH_out = PH_in[(PH_SIZE-ECC_SIZE-1):0] ^ (1<<15); end
8'h31 : begin {no_error, corrected_error, error} = 3'b010; PH_out = PH_in[(PH_SIZE-ECC_SIZE-1):0] ^ (1<<16); end
8'h32 : begin {no_error, corrected_error, error} = 3'b010; PH_out = PH_in[(PH_SIZE-ECC_SIZE-1):0] ^ (1<<17); end
8'h34 : begin {no_error, corrected_error, error} = 3'b010; PH_out = PH_in[(PH_SIZE-ECC_SIZE-1):0] ^ (1<<18); end
8'h38 : begin {no_error, corrected_error, error} = 3'b010; PH_out = PH_in[(PH_SIZE-ECC_SIZE-1):0] ^ (1<<19); end
8'h1F : begin {no_error, corrected_error, error} = 3'b010; PH_out = PH_in[(PH_SIZE-ECC_SIZE-1):0] ^ (1<<20); end
8'h2F : begin {no_error, corrected_error, error} = 3'b010; PH_out = PH_in[(PH_SIZE-ECC_SIZE-1):0] ^ (1<<21); end
8'h37 : begin {no_error, corrected_error, error} = 3'b010; PH_out = PH_in[(PH_SIZE-ECC_SIZE-1):0] ^ (1<<22); end
8'h3B : begin {no_error, corrected_error, error} = 3'b010; PH_out = PH_in[(PH_SIZE-ECC_SIZE-1):0] ^ (1<<23); end
8'h00 : begin {no_error, corrected_error, error} = 3'b100; PH_out = PH_in[(PH_SIZE-ECC_SIZE-1):0]; end
default: begin {no_error, corrected_error, error} = 3'b001; PH_out = PH_in[(PH_SIZE-ECC_SIZE-1):0]; end
endcase
end
endmodule