diff --git a/rtl/core/exception.sv b/rtl/core/exception.sv
index 0f85423..62fad1f 100644
--- a/rtl/core/exception.sv
+++ b/rtl/core/exception.sv
@@ -27,6 +27,10 @@
 `define MIE_MEIE_BIT            11
 `define MIE_MSIE_BIT            3
 
+`define DCSR_CAUSE_NONE         3'h0
+`define DCSR_CAUSE_STEP         3'h4
+`define DCSR_CAUSE_DBGREQ       3'h3
+`define DCSR_CAUSE_EBREAK       3'h1
 
 
 module exception (
@@ -82,13 +86,14 @@ module exception (
     localparam FAST_INT_OFFSET              = 44;
 
 
-    localparam S_IDLE       = 3'b001;
-    localparam S_W_MEPC     = 3'b010;
-    localparam S_ASSERT     = 3'b100;
+    localparam S_IDLE       = 4'b0001;
+    localparam S_W_MEPC     = 4'b0010;
+    localparam S_W_DCSR     = 4'b0100;
+    localparam S_ASSERT     = 4'b1000;
 
 
     reg debug_mode_d, debug_mode_q;
-    reg[2:0] state_d, state_q;
+    reg[3:0] state_d, state_q;
     reg[31:0] assert_addr_d, assert_addr_q;
     reg[31:0] return_addr_d, return_addr_q;
     reg csr_we;
@@ -179,9 +184,32 @@ module exception (
     assign int_or_exception_cause   = exception_req ? exception_cause  : interrupt_cause;
     assign int_or_exception_offset  = exception_req ? exception_offset : interrupt_offset;
 
-    wire debug_mode_req = ((~debug_mode_q) & debug_req_i & inst_valid_i) |
-                          (inst_ebreak_i & dcsr_i[15]) |
-                          (inst_ebreak_i & debug_mode_q);
+    reg enter_debug_cause_debugger_req;
+    reg enter_debug_cause_single_step;
+    reg enter_debug_cause_ebreak;
+    reg[2:0] dcsr_cause_d, dcsr_cause_q;
+
+    always @ (*) begin
+        enter_debug_cause_debugger_req = 1'b0;
+        enter_debug_cause_single_step = 1'b0;
+        enter_debug_cause_ebreak = 1'b0;
+        dcsr_cause_d = `DCSR_CAUSE_NONE;
+
+        if (inst_ebreak_i & debug_mode_q) begin
+            enter_debug_cause_ebreak = 1'b1;
+            dcsr_cause_d = `DCSR_CAUSE_EBREAK;
+        end else if ((~debug_mode_q) & debug_req_i & inst_valid_i) begin
+            enter_debug_cause_debugger_req = 1'b1;
+            dcsr_cause_d = `DCSR_CAUSE_DBGREQ;
+        end else if (inst_ebreak_i & dcsr_i[15]) begin
+            enter_debug_cause_single_step = 1'b1;
+            dcsr_cause_d = `DCSR_CAUSE_STEP;
+        end
+    end
+
+    wire debug_mode_req = enter_debug_cause_debugger_req |
+                          enter_debug_cause_single_step |
+                          enter_debug_cause_ebreak;
 
     assign stall_flag_o = ((state_q != S_IDLE) & (state_q != S_ASSERT)) |
                           (interrupt_req & global_int_en) | exception_req |
@@ -209,13 +237,13 @@ module exception (
                     state_d = S_W_MEPC;
                 end else if (debug_mode_req) begin
                     debug_mode_d = 1'b1;
-                    if (!inst_ebreak_i) begin
+                    if (enter_debug_cause_debugger_req) begin
                         csr_we = 1'b1;
                         csr_waddr = {20'h0, `CSR_DPC};
                         csr_wdata = inst_addr_i;
                     end
                     assert_addr_d = debug_halt_addr_i;
-                    state_d = S_ASSERT;
+                    state_d = S_W_DCSR;
                 end else if (inst_mret_i) begin
                     assert_addr_d = mepc_i;
                     state_d = S_ASSERT;
@@ -233,6 +261,13 @@ module exception (
                 state_d = S_ASSERT;
             end
 
+            S_W_DCSR: begin
+                csr_we = 1'b1;
+                csr_waddr = {20'h0, `CSR_DCSR};
+                csr_wdata = {dcsr_i[31:9], dcsr_cause_q, dcsr_i[5:0]};
+                state_d = S_ASSERT;
+            end
+
             S_ASSERT: begin
                 csr_we = 1'b0;
                 state_d = S_IDLE;
@@ -256,11 +291,13 @@ module exception (
             assert_addr_q <= 32'h0;
             debug_mode_q <= 1'b0;
             return_addr_q <= 32'h0;
+            dcsr_cause_q <= `DCSR_CAUSE_NONE;
         end else begin
             state_q <= state_d;
             assert_addr_q <= assert_addr_d;
             debug_mode_q <= debug_mode_d;
             return_addr_q <= return_addr_d;
+            dcsr_cause_q <= dcsr_cause_d;
         end
     end
 
diff --git a/rtl/debug/jtag_def.sv b/rtl/debug/jtag_def.sv
index 5828dbe..a558df6 100644
--- a/rtl/debug/jtag_def.sv
+++ b/rtl/debug/jtag_def.sv
@@ -68,6 +68,8 @@
 `define SBData1             6'h3D
 `define SBData2             6'h3E
 `define SBData3             6'h3F
+`define HaltSum0            6'h40
+`define HaltSum1            6'h13
 
 // dmstatus bit index
 `define Impebreak           22
diff --git a/rtl/debug/jtag_dm.sv b/rtl/debug/jtag_dm.sv
index 9780dd1..682631f 100644
--- a/rtl/debug/jtag_dm.sv
+++ b/rtl/debug/jtag_dm.sv
@@ -252,6 +252,8 @@ module jtag_dm #(
                             cmderr_d = CmdErrorBusy;
                         end
                     end
+                    `HaltSum0: dm_resp_data_d = {31'h0, halted};
+                    `HaltSum1: dm_resp_data_d = {31'h0, halted};
                     default: dm_resp_data_d = 32'h0;
                 endcase
             // write
@@ -479,7 +481,7 @@ module jtag_dm #(
         .resumereq_i(resumereq),
         .haltreq_i(debug_req_o),
 
-        .progbuf_i(),
+        .progbuf_i(progbuf_q),
         .data_i(data0_q),
         .data_o(data0),
         .data_valid_o(data_valid),
diff --git a/sim/jtag_compliance_test.cfg b/sim/jtag_compliance_test.cfg
index 9b7b5f6..5512cad 100644
--- a/sim/jtag_compliance_test.cfg
+++ b/sim/jtag_compliance_test.cfg
@@ -14,7 +14,7 @@ foreach t [jtag names] {
 }
 
 set _TARGETNAME $_CHIPNAME.cpu
-target create $_TARGETNAME riscv -chain-position $_TARGETNAME
+target create $_TARGETNAME riscv -chain-position $_TARGETNAME -rtos riscv
 
 riscv set_reset_timeout_sec 2000
 riscv set_command_timeout_sec 2000