| // 16-bit ones-complement checksum calculator | |
| // Applies to all of IP header, ICMP, and UDP checksums | |
| // Well, difficult to use with UDP because of its pathological | |
| // inclusion of _two_ copies of the UDP length. | |
| // mostly cribbed from core/assemble_eth.v | |
| module ones_chksum( | |
| input clk, | |
| input clear, | |
| input gate, | |
| input [7:0] din, | |
| output [7:0] sum, | |
| output all_ones | |
| ); | |
| reg [7:0] chksum=0, chksum1=0; | |
| reg chksum_carry=0; | |
| always @(posedge clk) begin | |
| if (clear) {chksum_carry, chksum} <= 9'h0; | |
| else if (gate) {chksum_carry, chksum} <= | |
| chksum1 + din + chksum_carry; | |
| if (clear) chksum1 <= 8'h0; | |
| else if (gate) chksum1 <= chksum; | |
| end | |
| assign sum = ~(chksum1 + chksum_carry); | |
| assign all_ones = &chksum; | |
| endmodule | |