diff --git a/fw/rtl/mcu/mcu_top.sv b/fw/rtl/mcu/mcu_top.sv
index 9e025df..76e9996 100644
--- a/fw/rtl/mcu/mcu_top.sv
+++ b/fw/rtl/mcu/mcu_top.sv
@@ -356,7 +356,8 @@ module mcu_top (
         REG_DD_DRIVE_ID,
         REG_VENDOR_SCR,
         REG_VENDOR_DATA,
-        REG_DEBUG
+        REG_DEBUG_0,
+        REG_DEBUG_1
     } reg_address_e;
 
     logic bootloader_skip;
@@ -631,10 +632,14 @@ module mcu_top (
                     reg_rdata <= vendor_scb.data_rdata;
                 end
 
-                REG_DEBUG: begin
+                REG_DEBUG_0: begin
+                    reg_rdata <= n64_scb.pi_debug[31:0];
+                end
+
+                REG_DEBUG_1: begin
                     reg_rdata <= {
                         28'd0,
-                        n64_scb.pi_debug
+                        n64_scb.pi_debug[35:32]
                     };
                 end
             endcase
diff --git a/fw/rtl/n64/n64_pi.sv b/fw/rtl/n64/n64_pi.sv
index e268c41..e15da47 100644
--- a/fw/rtl/n64/n64_pi.sv
+++ b/fw/rtl/n64/n64_pi.sv
@@ -122,6 +122,18 @@ module n64_pi (
     end
 
 
+    // Debug: last accessed PI address
+
+    always_ff @(posedge clk) begin
+        if (aleh_op) begin
+            n64_scb.pi_debug[31:16] <= n64_pi_dq_in;
+        end
+        if (alel_op) begin
+            n64_scb.pi_debug[15:0] <= n64_pi_dq_in;
+        end
+    end
+
+
     // Address decoding
 
     const bit [31:0] DDIPL_OFFSET       = 32'h03BC_0000;
@@ -289,8 +301,8 @@ module n64_pi (
     always_ff @(posedge clk) begin
         read_fifo_read <= 1'b0;
 
-        if (reset) begin
-            n64_scb.pi_debug[1:0] <= 2'b00;
+        if (!pi_reset) begin
+            n64_scb.pi_debug[33:32] <= 2'b00;
         end
 
         if (reset || !pi_reset || alel_op) begin
@@ -301,9 +313,9 @@ module n64_pi (
             if (read_op) begin
                 if (read_fifo_empty) begin
                     read_fifo_wait <= 1'b1;
-                    n64_scb.pi_debug[0] <= 1'b1;
+                    n64_scb.pi_debug[32] <= 1'b1;
                     if (read_fifo_wait) begin
-                        n64_scb.pi_debug[1] <= 1'b1;
+                        n64_scb.pi_debug[33] <= 1'b1;
                     end
                 end else begin
                     read_fifo_read <= 1'b1;
@@ -356,8 +368,8 @@ module n64_pi (
     always_ff @(posedge clk) begin
         write_fifo_write <= 1'b0;
 
-        if (reset) begin
-            n64_scb.pi_debug[3:2] <= 2'b00;
+        if (!pi_reset) begin
+            n64_scb.pi_debug[35:34] <= 2'b00;
         end
 
         if (reset) begin
@@ -368,9 +380,9 @@ module n64_pi (
             if (write_op) begin
                 if (write_fifo_full) begin
                     write_fifo_wait <= 1'b1;
-                    n64_scb.pi_debug[2] <= 1'b1;
+                    n64_scb.pi_debug[34] <= 1'b1;
                     if (write_fifo_wait) begin
-                        n64_scb.pi_debug[3] <= 1'b1;
+                        n64_scb.pi_debug[35] <= 1'b1;
                     end
                 end else begin
                     write_fifo_write <= 1'b1;
diff --git a/fw/rtl/n64/n64_scb.sv b/fw/rtl/n64/n64_scb.sv
index 7c22732..c61f103 100644
--- a/fw/rtl/n64/n64_scb.sv
+++ b/fw/rtl/n64/n64_scb.sv
@@ -53,7 +53,7 @@ interface n64_scb ();
 
     logic pi_sdram_active;
     logic pi_flash_active;
-    logic [3:0] pi_debug;
+    logic [35:0] pi_debug;
 
     modport controller (
         input n64_reset,
diff --git a/sw/controller/src/cfg.c b/sw/controller/src/cfg.c
index 9dc608c..8481e84 100644
--- a/sw/controller/src/cfg.c
+++ b/sw/controller/src/cfg.c
@@ -569,7 +569,8 @@ void cfg_process (void) {
                 break;
 
             case '?':
-                args[0] = fpga_reg_get(REG_DEBUG);
+                args[0] = fpga_reg_get(REG_DEBUG_0);
+                args[1] = fpga_reg_get(REG_DEBUG_1);
                 break;
 
             default:
diff --git a/sw/controller/src/fpga.h b/sw/controller/src/fpga.h
index a6cec0d..28a4979 100644
--- a/sw/controller/src/fpga.h
+++ b/sw/controller/src/fpga.h
@@ -52,7 +52,8 @@ typedef enum {
     REG_DD_DRIVE_ID,
     REG_VENDOR_SCR,
     REG_VENDOR_DATA,
-    REG_DEBUG
+    REG_DEBUG_0,
+    REG_DEBUG_1,
 } fpga_reg_t;
 
 
diff --git a/sw/controller/src/usb.c b/sw/controller/src/usb.c
index ea8fa27..ca73e75 100644
--- a/sw/controller/src/usb.c
+++ b/sw/controller/src/usb.c
@@ -288,8 +288,9 @@ static void usb_rx_process (void) {
             case '?':
                 p.rx_state = RX_STATE_IDLE;
                 p.response_pending = true;
-                p.response_info.data_length = 4;
-                p.response_info.data[0] = fpga_reg_get(REG_DEBUG);
+                p.response_info.data_length = 8;
+                p.response_info.data[0] = fpga_reg_get(REG_DEBUG_0);
+                p.response_info.data[1] = fpga_reg_get(REG_DEBUG_1);
                 break;
 
             default: