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[rtl] Fix xprop issues in cs_registers

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Alter how logic for csr_wreq was written to not propagate X when using
certain more pessimistic modes of x propagation in simulation.
This commit is contained in:
Greg Chadwick 2020-04-06 16:29:32 +01:00
parent cb8afccb7c
commit 0852120462
1 changed files with 7 additions and 10 deletions
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17
rtl/ibex_cs_registers.sv
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@ -620,23 +620,20 @@ module ibex_cs_registers #(
// CSR operation logic
always_comb begin
csr_wreq = csr_op_en_i;
unique case (csr_op_i)
CSR_OP_WRITE: csr_wdata_int = csr_wdata_i;
CSR_OP_SET: csr_wdata_int = csr_wdata_i | csr_rdata_o;
CSR_OP_CLEAR: csr_wdata_int = ~csr_wdata_i & csr_rdata_o;
CSR_OP_READ: begin
csr_wdata_int = csr_wdata_i;
csr_wreq = 1'b0;
end
default: begin
csr_wdata_int = csr_wdata_i;
csr_wreq = 1'b0;
end
CSR_OP_READ: csr_wdata_int = csr_wdata_i;
default: csr_wdata_int = csr_wdata_i;
endcase
end
assign csr_wreq = csr_op_en_i &
(csr_op_i inside {CSR_OP_WRITE,
CSR_OP_SET,
CSR_OP_CLEAR});
// only write CSRs during one clock cycle
assign csr_we_int = csr_wreq & ~illegal_csr_insn_o;