File size: 1,722 Bytes
49812da | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 | // See LICENSE.SiFive for license details.
/** This black-boxes an Async Reset
* Reg.
*
* Because Chisel doesn't support
* parameterized black boxes,
* we unfortunately have to
* instantiate a number of these.
*
* We also have to hard-code the set/reset.
*
* Do not confuse an asynchronous
* reset signal with an asynchronously
* reset reg. You should still
* properly synchronize your reset
* deassertion.
*
* @param d Data input
* @param q Data Output
* @param clk Clock Input
* @param rst Reset Input
* @param en Write Enable Input
*
*/
`ifdef RANDOMIZE_GARBAGE_ASSIGN
`define RANDOMIZE
`endif
`ifdef RANDOMIZE_INVALID_ASSIGN
`define RANDOMIZE
`endif
`ifdef RANDOMIZE_REG_INIT
`define RANDOMIZE
`endif
`ifdef RANDOMIZE_MEM_INIT
`define RANDOMIZE
`endif
module AsyncResetReg (d, q, en, clk, rst);
parameter RESET_VALUE = 0;
input wire d;
output reg q;
input wire en;
input wire clk;
input wire rst;
// There is a lot of initialization
// here you don't normally find in Verilog
// async registers because of scenarios in which reset
// is not actually asserted cleanly at time 0,
// and we want to make sure to properly model
// that, yet Chisel codebase is absolutely intolerant
// of Xs.
`ifndef SYNTHESIS
initial begin:B0
`ifdef RANDOMIZE
integer initvar;
reg [31:0] _RAND;
_RAND = {1{$random}};
q = _RAND[0];
`endif // RANDOMIZE
if (rst) begin
q = RESET_VALUE[0];
end
end
`endif
always @(posedge clk or posedge rst) begin
if (rst) begin
q <= RESET_VALUE[0];
end else if (en) begin
q <= d;
end
end
endmodule // AsyncResetReg
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