Implement single-stepping

1 files changed, 6 insertions, 2 deletions

diff --git a/rtl/core/porch/porch.sv b/rtl/core/porch/porch.sv
index 238da88..4369836 100644
--- a/rtl/core/porch/porch.sv
+++ b/rtl/core/porch/porch.sv
@@ -9,6 +9,7 @@ module core_porch
 	input  psr_flags   flags,
 
 	input  word        fetch_insn,
+	input  logic       fetch_nop,
 	input  ptr         fetch_insn_pc,
 	                   fetch_head,
 	input  insn_decode fetch_dec,
@@ -18,12 +19,13 @@ module core_porch
 	output insn_decode dec
 );
 
-	logic execute, conditional, undefined;
+	logic execute, conditional, undefined, nop;
 	insn_decode hold_dec;
 
 	always_comb begin
 		dec = hold_dec;
-		dec.ctrl.execute = !flush && dec.ctrl.execute && execute;
+		dec.ctrl.nop = nop;
+		dec.ctrl.execute = !flush && dec.ctrl.execute && execute && !nop;
 		dec.ctrl.undefined = !flush && (dec.ctrl.undefined || undefined);
 		dec.ctrl.conditional = !flush && (dec.ctrl.conditional || conditional);
 	end
@@ -35,10 +37,12 @@ module core_porch
 
 	always_ff @(posedge clk or negedge rst_n)
 		if(!rst_n) begin
+			nop <= 0; // Even though it is a NOP
 			insn <= `NOP;
 			insn_pc <= 0;
 			hold_dec <= {$bits(hold_dec){1'b0}};
 		end else if(flush || !stall) begin
+			nop <= flush ? 1 : fetch_nop;
 			insn <= flush ? `NOP : fetch_insn;
 			insn_pc <= flush ? fetch_head : fetch_insn_pc;
 			hold_dec <= fetch_dec;