diff --git a/core_debug.vhdl b/core_debug.vhdl
index 9efaa7c..09e3e48 100644
--- a/core_debug.vhdl
+++ b/core_debug.vhdl
@@ -91,6 +91,7 @@ architecture behave of core_debug is
     -- Log buffer address and data registers
     constant DBG_CORE_LOG_ADDR       : std_ulogic_vector(3 downto 0) := "0110";
     constant DBG_CORE_LOG_DATA       : std_ulogic_vector(3 downto 0) := "0111";
+    constant DBG_CORE_LOG_TRIGGER    : std_ulogic_vector(3 downto 0) := "1000";
 
     constant LOG_INDEX_BITS : natural := log2(LOG_LENGTH);
 
@@ -108,6 +109,8 @@ architecture behave of core_debug is
 
     signal log_dmi_addr : std_ulogic_vector(31 downto 0) := (others => '0');
     signal log_dmi_data : std_ulogic_vector(63 downto 0) := (others => '0');
+    signal log_dmi_trigger : std_ulogic_vector(63 downto 0) := (others => '0');
+    signal do_log_trigger : std_ulogic := '0';
     signal do_dmi_log_rd : std_ulogic;
     signal dmi_read_log_data : std_ulogic;
     signal dmi_read_log_data_1 : std_ulogic;
@@ -133,6 +136,7 @@ begin
         dbg_gpr_data    when DBG_CORE_GSPR_DATA,
         log_write_addr & log_dmi_addr when DBG_CORE_LOG_ADDR,
         log_dmi_data    when DBG_CORE_LOG_DATA,
+        log_dmi_trigger when DBG_CORE_LOG_TRIGGER,
 	(others => '0') when others;
 
     -- DMI writes
@@ -149,6 +153,9 @@ begin
 		stopping <= '0';
 		terminated <= '0';
 	    else
+                if do_log_trigger = '1' then
+                    log_dmi_trigger(1) <= '1';
+                end if;
 		-- Edge detect on dmi_req for 1-shot pulses
 		dmi_req_1 <= dmi_req;
 		if dmi_req = '1' and dmi_req_1 = '0' then
@@ -180,6 +187,8 @@ begin
                         elsif dmi_addr = DBG_CORE_LOG_ADDR then
                             log_dmi_addr <= dmi_din(31 downto 0);
                             do_dmi_log_rd <= '1';
+                        elsif dmi_addr = DBG_CORE_LOG_TRIGGER then
+                            log_dmi_trigger <= dmi_din;
 			end if;
 		    else
 			report("DMI read from " & to_string(dmi_addr));
@@ -246,7 +255,7 @@ begin
 
     begin
         -- Use MSB of read addresses to stop the logging
-        log_wr_enable <= not (log_read_addr(31) or log_dmi_addr(31));
+        log_wr_enable <= not (log_read_addr(31) or log_dmi_addr(31) or log_dmi_trigger(1));
 
         log_ram: process(clk)
         begin
@@ -285,6 +294,12 @@ begin
                 end if;
                 log_dmi_read_done <= log_dmi_reading;
                 log_dmi_reading <= do_dmi_log_rd;
+                do_log_trigger <= '0';
+                if log_data(42) = log_dmi_trigger(63) and
+                    log_data(41 downto 0) = log_dmi_trigger(43 downto 2) and
+                    log_dmi_trigger(0) = '1' then
+                    do_log_trigger <= '1';
+                end if;
             end if;
         end process;
         log_write_addr(LOG_INDEX_BITS - 1 downto 0) <= std_ulogic_vector(log_wr_ptr);
diff --git a/scripts/mw_debug/mw_debug.c b/scripts/mw_debug/mw_debug.c
index d03e61c..4179264 100644
--- a/scripts/mw_debug/mw_debug.c
+++ b/scripts/mw_debug/mw_debug.c
@@ -44,6 +44,7 @@
 
 #define DBG_LOG_ADDR		0x16
 #define DBG_LOG_DATA		0x17
+#define DBG_LOG_TRIGGER		0x18
 
 static bool debug;
 
@@ -466,8 +467,11 @@ static void gpr_read(uint64_t reg, uint64_t count)
 
 static void mem_read(uint64_t addr, uint64_t count)
 {
-	uint64_t data;
-	int i, rc;
+	union {
+		uint64_t data;
+		unsigned char c[8];
+	} u;
+	int i, j, rc;
 
 	rc = dmi_write(DBG_WB_CTRL, 0x7ff);
 	if (rc < 0)
@@ -476,12 +480,15 @@ static void mem_read(uint64_t addr, uint64_t count)
 	if (rc < 0)
 		return;
 	for (i = 0; i < count; i++) {
-		rc = dmi_read(DBG_WB_DATA, &data);
+		rc = dmi_read(DBG_WB_DATA, &u.data);
 		if (rc < 0)
 			return;
-		printf("%016llx: %016llx\n",
+		printf("%016llx: %016llx  ",
 		       (unsigned long long)addr,
-		       (unsigned long long)data);
+		       (unsigned long long)u.data);
+		for (j = 0; j < 8; ++j)
+			putchar(u.c[j] >= 0x20 && u.c[j] < 0x7f? u.c[j]: '.');
+		putchar('\n');
 		addr += 8;
 	}
 }
@@ -622,6 +629,28 @@ static void log_dump(const char *filename)
 	check(dmi_write(DBG_LOG_ADDR, orig_laddr), "writing LOG_ADDR");
 }
 
+static void ltrig_show(void)
+{
+	uint64_t trig;
+
+	check(dmi_read(DBG_LOG_TRIGGER, &trig), "reading LOG_TRIGGER");
+	if (trig & 1)
+		printf("log stop trigger at %" PRIx64, trig & ~3);
+	else
+		printf("log stop trigger disabled");
+	printf(", %striggered\n", (trig & 2? "": "not "));
+}
+
+static void ltrig_off(void)
+{
+	check(dmi_write(DBG_LOG_TRIGGER, 0), "writing LOG_TRIGGER");
+}
+
+static void ltrig_set(uint64_t addr)
+{
+	check(dmi_write(DBG_LOG_TRIGGER, (addr & ~(uint64_t)2) | 1), "writing LOG_TRIGGER");
+}
+
 static void usage(const char *cmd)
 {
 	fprintf(stderr, "Usage: %s -b <jtag|sim> <command> <args>\n", cmd);
@@ -651,6 +680,9 @@ static void usage(const char *cmd)
 	fprintf(stderr, "  lstart			start logging\n");
 	fprintf(stderr, "  lstop			stop logging\n");
 	fprintf(stderr, "  ldump <file>			dump log to file\n");
+	fprintf(stderr, "  ltrig 			show logging stop trigger status\n");
+	fprintf(stderr, "  ltrig off 			clear logging stop trigger address\n");
+	fprintf(stderr, "  ltrig <addr>			set logging stop trigger address\n");
 
 	fprintf(stderr, "\n");
 	fprintf(stderr, " JTAG:\n");
@@ -801,9 +833,20 @@ int main(int argc, char *argv[])
 				usage(argv[0]);
 			filename = argv[++i];
 			log_dump(filename);
+		} else if (strcmp(argv[i], "ltrig") == 0) {
+			uint64_t addr;
+
+			if ((i+1) >= argc)
+				ltrig_show();
+			else if (strcmp(argv[++i], "off") == 0)
+				ltrig_off();
+			else {
+				addr = strtoul(argv[i], NULL, 16);
+				ltrig_set(addr);
+			}
 		} else {
 			fprintf(stderr, "Unknown command %s\n", argv[i]);
-			exit(1);
+			usage(argv[0]);
 		}
 	}
 	core_status();