diff --git a/artiq/coredevice/runtime.py b/artiq/coredevice/runtime.py
index 28e755642..1136d41eb 100644
--- a/artiq/coredevice/runtime.py
+++ b/artiq/coredevice/runtime.py
@@ -12,6 +12,8 @@ llvm.initialize_all_targets()
 llvm.initialize_all_asmprinters()
 
 _syscalls = {
+    "watchdog_set": "i:i",
+    "watchdog_clear": "i:n",
     "rtio_set_o": "Iii:n",
     "rtio_set_oe": "Iib:n",
     "rtio_set_sensitivity": "Iii:n",
diff --git a/artiq/transforms/lower_units.py b/artiq/transforms/lower_units.py
index f86f24a90..eef71e564 100644
--- a/artiq/transforms/lower_units.py
+++ b/artiq/transforms/lower_units.py
@@ -120,7 +120,7 @@ class _UnitsLowerer(ast.NodeTransformer):
             else:
                 if any(hasattr(arg, "unit") for arg in node.args):
                     raise units.DimensionError
-        elif node.func.id in ("delay", "at", "time_to_cycles"):
+        elif node.func.id in ("delay", "at", "time_to_cycles", "watchdog"):
             if getattr(node.args[0], "unit", None) != "s":
                 raise units.DimensionError
         elif node.func.id == "check_unit":
diff --git a/artiq/transforms/quantize_time.py b/artiq/transforms/quantize_time.py
index 6f8fe05e8..835dcd780 100644
--- a/artiq/transforms/quantize_time.py
+++ b/artiq/transforms/quantize_time.py
@@ -7,8 +7,7 @@ It does so by inserting multiplication/division/rounding operations around
 those calls.
 
 The time_to_cycles and cycles_to_time core language functions are also
-implemented here.
-
+implemented here, as well as watchdog to syscall conversion.
 """
 
 import ast
@@ -47,6 +46,7 @@ def _cycles_to_time(ref_period, node):
 class _TimeQuantizer(ast.NodeTransformer):
     def __init__(self, ref_period):
         self.ref_period = ref_period
+        self.watchdog_id_counter = 0
 
     def visit_Call(self, node):
         funcname = node.func.id
@@ -78,6 +78,51 @@ class _TimeQuantizer(ast.NodeTransformer):
             self.generic_visit(node)
             return node
 
+    def visit_With(self, node):
+        self.generic_visit(node)
+        if (isinstance(node.items[0].context_expr, ast.Call)
+                and node.items[0].context_expr.func.id == "watchdog"):
+
+            idname = "__watchdog_id_" + str(self.watchdog_id_counter)
+            self.watchdog_id_counter += 1
+
+            time = ast.BinOp(left=node.items[0].context_expr.args[0],
+                             op=ast.Mult(),
+                             right=ast.Num(1000))
+            time_int = ast.Call(
+                func=ast.Name("round", ast.Load()),
+                args=[time],
+                keywords=[], starargs=None, kwargs=None)
+            syscall_set = ast.Call(
+                func=ast.Name("syscall", ast.Load()),
+                args=[ast.Str("watchdog_set"), time_int],
+                keywords=[], starargs=None, kwargs=None)
+            stmt_set = ast.copy_location(
+                ast.Assign(targets=[ast.Name(idname, ast.Store())],
+                           value=syscall_set),
+                node)
+
+            syscall_clear = ast.Call(
+                func=ast.Name("syscall", ast.Load()),
+                args=[ast.Str("watchdog_clear"),
+                              ast.Name(idname, ast.Load())],
+                keywords=[], starargs=None, kwargs=None)
+            stmt_clear = ast.copy_location(ast.Expr(syscall_clear), node)
+
+            node.items[0] = ast.withitem(
+                context_expr=ast.Name(id="sequential",
+                ctx=ast.Load()),
+                optional_vars=None)
+            node.body = [
+                stmt_set,
+                ast.Try(body=node.body,
+                        handlers=[],
+                        orelse=[],
+                        finalbody=[stmt_clear])
+            ]
+        return node
+
+
 
 def quantize_time(func_def, ref_period):
     _TimeQuantizer(ref_period).visit(func_def)
diff --git a/artiq/transforms/tools.py b/artiq/transforms/tools.py
index 098458bb0..d9daf838f 100644
--- a/artiq/transforms/tools.py
+++ b/artiq/transforms/tools.py
@@ -8,7 +8,7 @@ from artiq.language import units
 embeddable_funcs = (
     core_language.delay, core_language.at, core_language.now,
     core_language.time_to_cycles, core_language.cycles_to_time,
-    core_language.syscall,
+    core_language.syscall, core_language.watchdog,
     range, bool, int, float, round, len,
     core_language.int64, core_language.round64,
     Fraction, units.Quantity, units.check_unit, core_language.EncodedException
diff --git a/soc/runtime/Makefile b/soc/runtime/Makefile
index 8f5880e96..1b95bd727 100644
--- a/soc/runtime/Makefile
+++ b/soc/runtime/Makefile
@@ -1,6 +1,6 @@
 include $(MSCDIR)/software/common.mak
 
-OBJECTS := isr.o flash_storage.o elf_loader.o services.o session.o log.o test_mode.o kloader.o mailbox.o ksupport_data.o main.o
+OBJECTS := isr.o flash_storage.o clock.o elf_loader.o services.o session.o log.o test_mode.o kloader.o mailbox.o ksupport_data.o main.o
 OBJECTS_KSUPPORT := ksupport.o exception_jmp.o exceptions.o mailbox.o bridge.o rtio.o dds.o
 
 CFLAGS += -Ilwip/src/include -Iliblwip
diff --git a/soc/runtime/clock.c b/soc/runtime/clock.c
new file mode 100644
index 000000000..6b3946790
--- /dev/null
+++ b/soc/runtime/clock.c
@@ -0,0 +1,81 @@
+#include <generated/csr.h>
+
+#include "log.h"
+#include "clock.h"
+
+static int clkdiv;
+
+void clock_init(void)
+{
+    timer0_en_write(0);
+    timer0_load_write(0x7fffffffffffffffLL);
+    timer0_reload_write(0x7fffffffffffffffLL);
+    timer0_en_write(1);
+    clkdiv = identifier_frequency_read()/1000;
+}
+
+long long int clock_get_ms(void)
+{
+    long long int clock_sys;
+    long long int clock_ms;
+
+    timer0_update_value_write(1);
+    clock_sys = 0x7fffffffffffffffLL - timer0_value_read();
+
+    clock_ms = clock_sys/clkdiv;
+    return clock_ms;
+}
+
+struct watchdog {
+    int active;
+    long long int threshold;
+};
+
+static struct watchdog watchdogs[MAX_WATCHDOGS];
+
+void watchdog_init(void)
+{
+    int i;
+
+    for(i=0;i<MAX_WATCHDOGS;i++)
+        watchdogs[i].active = 0;
+}
+
+int watchdog_set(int ms)
+{
+    int i, id;
+
+    id = -1;
+    for(i=0;i<MAX_WATCHDOGS;i++)
+        if(!watchdogs[i].active) {
+            id = i;
+            break;
+        }
+    if(id < 0) {
+        log("Failed to add watchdog");
+        return id;
+    }
+
+    watchdogs[id].active = 1;
+    watchdogs[id].threshold = clock_get_ms() + ms;
+    return id;
+}
+
+void watchdog_clear(int id)
+{
+    if((id < 0) || (id >= MAX_WATCHDOGS))
+        return;
+    watchdogs[id].active = 0;
+}
+
+int watchdog_expired(void)
+{
+    int i;
+    long long int t;
+
+    t = 0x7fffffffffffffffLL;
+    for(i=0;i<MAX_WATCHDOGS;i++)
+        if(watchdogs[i].active && (watchdogs[i].threshold < t))
+            t = watchdogs[i].threshold;
+    return clock_get_ms() > t;
+}
diff --git a/soc/runtime/clock.h b/soc/runtime/clock.h
new file mode 100644
index 000000000..70de5e5b7
--- /dev/null
+++ b/soc/runtime/clock.h
@@ -0,0 +1,14 @@
+#ifndef __CLOCK_H
+#define __CLOCK_H
+
+void clock_init(void);
+long long int clock_get_ms(void);
+
+#define MAX_WATCHDOGS 16
+
+void watchdog_init(void);
+int watchdog_set(int ms);
+void watchdog_clear(int id);
+int watchdog_expired(void);
+
+#endif /* __CLOCK_H */
diff --git a/soc/runtime/gen_service_table.py b/soc/runtime/gen_service_table.py
index 5c070848f..6d200757f 100755
--- a/soc/runtime/gen_service_table.py
+++ b/soc/runtime/gen_service_table.py
@@ -8,6 +8,8 @@ from elftools.elf.elffile import ELFFile
 services = [
     ("syscalls", [
         ("rpc", "rpc"),
+        ("watchdog_set", "watchdog_set"),
+        ("watchdog_clear", "watchdog_clear"),
         ("rtio_set_o", "rtio_set_o"),
         ("rtio_set_oe", "rtio_set_oe"),
         ("rtio_set_sensitivity", "rtio_set_sensitivity"),
diff --git a/soc/runtime/ksupport.c b/soc/runtime/ksupport.c
index 81b5cd25c..5330c54d8 100644
--- a/soc/runtime/ksupport.c
+++ b/soc/runtime/ksupport.c
@@ -7,6 +7,8 @@
 #include "rtio.h"
 #include "dds.h"
 
+/* for the prototypes for watchdog_set() and watchdog_clear() */
+#include "clock.h"
 /* for the prototype for rpc() */
 #include "session.h"
 /* for the prototype for log() */
@@ -61,6 +63,34 @@ int main(void)
     while(1);
 }
 
+int watchdog_set(int ms)
+{
+    struct msg_watchdog_set_request request;
+    struct msg_watchdog_set_reply *reply;
+    int id;
+
+    request.type = MESSAGE_TYPE_WATCHDOG_SET_REQUEST;
+    request.ms = ms;
+    mailbox_send_and_wait(&request);
+
+    reply = mailbox_wait_and_receive();
+    if(reply->type != MESSAGE_TYPE_WATCHDOG_SET_REPLY)
+        exception_raise(EID_INTERNAL_ERROR);
+    id = reply->id;
+    mailbox_acknowledge();
+
+    return id;
+}
+
+void watchdog_clear(int id)
+{
+    struct msg_watchdog_clear request;
+
+    request.type = MESSAGE_TYPE_WATCHDOG_CLEAR;
+    request.id = id;
+    mailbox_send_and_wait(&request);
+}
+
 int rpc(int rpc_num, ...)
 {
     struct msg_rpc_request request;
diff --git a/soc/runtime/main.c b/soc/runtime/main.c
index e664c7b57..29a4fc378 100644
--- a/soc/runtime/main.c
+++ b/soc/runtime/main.c
@@ -21,26 +21,16 @@
 #include <lwip/timers.h>
 #endif
 
+#include "clock.h"
 #include "test_mode.h"
 #include "session.h"
 
 #ifdef CSR_ETHMAC_BASE
 unsigned char macadr[6] = {0x10, 0xe2, 0xd5, 0x00, 0x00, 0x00};
 
-static int clkdiv;
-
 u32_t sys_now(void)
 {
-    static unsigned long long int clock_sys;
-    u32_t clock_ms;
-
-    timer0_update_value_write(1);
-    clock_sys += 0xffffffff - timer0_value_read();
-    timer0_en_write(0);
-    timer0_en_write(1);
-
-    clock_ms = clock_sys/clkdiv;
-    return clock_ms;
+    return clock_get_ms();
 }
 
 static struct netif netif;
@@ -60,12 +50,6 @@ static void network_init(void)
     struct ip4_addr netmask;
     struct ip4_addr gateway_ip;
 
-    timer0_en_write(0);
-    timer0_load_write(0xffffffff);
-    timer0_reload_write(0xffffffff);
-    timer0_en_write(1);
-    clkdiv = identifier_frequency_read()/1000;
-
     IP4_ADDR(&local_ip, 192, 168, 0, 42);
     IP4_ADDR(&netmask, 255, 255, 255, 0);
     IP4_ADDR(&gateway_ip, 192, 168, 0, 1);
@@ -276,6 +260,7 @@ static void kserver_service(void)
 
 static void regular_main(void)
 {
+    clock_init();
     network_init();
     kserver_init();
 
@@ -332,6 +317,8 @@ static void serial_service(void)
 
 static void regular_main(void)
 {
+    clock_init();
+
     /* Open the session for the serial control. */
     session_start();
     while(1)
diff --git a/soc/runtime/messages.h b/soc/runtime/messages.h
index 8c48a0946..6706abbf7 100644
--- a/soc/runtime/messages.h
+++ b/soc/runtime/messages.h
@@ -6,6 +6,9 @@
 enum {
     MESSAGE_TYPE_FINISHED,
     MESSAGE_TYPE_EXCEPTION,
+    MESSAGE_TYPE_WATCHDOG_SET_REQUEST,
+    MESSAGE_TYPE_WATCHDOG_SET_REPLY,
+    MESSAGE_TYPE_WATCHDOG_CLEAR,
     MESSAGE_TYPE_RPC_REQUEST,
     MESSAGE_TYPE_RPC_REPLY,
     MESSAGE_TYPE_LOG,
@@ -32,6 +35,21 @@ struct msg_exception {
     long long int eparams[3];
 };
 
+struct msg_watchdog_set_request {
+    int type;
+    int ms;
+};
+
+struct msg_watchdog_set_reply {
+    int type;
+    int id;
+};
+
+struct msg_watchdog_clear {
+    int type;
+    int id;
+};
+
 struct msg_rpc_request {
     int type;
     int rpc_num;
diff --git a/soc/runtime/services.c b/soc/runtime/services.c
index 720df7afa..35cbf3f57 100644
--- a/soc/runtime/services.c
+++ b/soc/runtime/services.c
@@ -2,6 +2,7 @@
 
 #include "elf_loader.h"
 #include "session.h"
+#include "clock.h"
 #include "rtio.h"
 #include "dds.h"
 #include "exceptions.h"
diff --git a/soc/runtime/session.c b/soc/runtime/session.c
index 57436cdf2..7c116ee46 100644
--- a/soc/runtime/session.c
+++ b/soc/runtime/session.c
@@ -7,6 +7,7 @@
 #include "mailbox.h"
 #include "messages.h"
 
+#include "clock.h"
 #include "log.h"
 #include "kloader.h"
 #include "exceptions.h"
@@ -282,6 +283,7 @@ static int process_input(void)
                 break;
             }
 
+            watchdog_init();
             kloader_start_user_kernel(k);
             user_kernel_state = USER_KERNEL_RUNNING;
             break;
@@ -364,6 +366,9 @@ int session_input(void *data, int len)
     return consumed;
 }
 
+#include <generated/mem.h>
+#define KERNELCPU_MAILBOX MMPTR(MAILBOX_BASE)
+
 /* assumes output buffer is empty when called */
 static int process_kmsg(struct msg_base *umsg)
 {
@@ -379,6 +384,7 @@ static int process_kmsg(struct msg_base *umsg)
 
             kloader_stop_kernel();
             user_kernel_state = USER_KERNEL_LOADED;
+            mailbox_acknowledge();
             break;
         case MESSAGE_TYPE_EXCEPTION: {
             struct msg_exception *msg = (struct msg_exception *)umsg;
@@ -390,6 +396,23 @@ static int process_kmsg(struct msg_base *umsg)
 
             kloader_stop_kernel();
             user_kernel_state = USER_KERNEL_LOADED;
+            mailbox_acknowledge();
+            break;
+        }
+        case MESSAGE_TYPE_WATCHDOG_SET_REQUEST: {
+            struct msg_watchdog_set_request *msg = (struct msg_watchdog_set_request *)umsg;
+            struct msg_watchdog_set_reply reply;
+
+            reply.type = MESSAGE_TYPE_WATCHDOG_SET_REPLY;
+            reply.id = watchdog_set(msg->ms);
+            mailbox_send_and_wait(&reply);
+            break;
+        }
+        case MESSAGE_TYPE_WATCHDOG_CLEAR: {
+            struct msg_watchdog_clear *msg = (struct msg_watchdog_clear *)umsg;
+
+            watchdog_clear(msg->id);
+            mailbox_acknowledge();
             break;
         }
         case MESSAGE_TYPE_RPC_REQUEST: {
@@ -398,12 +421,14 @@ static int process_kmsg(struct msg_base *umsg)
             if(!send_rpc_request(msg->rpc_num, msg->args))
                 return 0;
             user_kernel_state = USER_KERNEL_WAIT_RPC;
+            mailbox_acknowledge();
             break;
         }
         case MESSAGE_TYPE_LOG: {
             struct msg_log *msg = (struct msg_log *)umsg;
 
             log(msg->fmt, msg->args);
+            mailbox_acknowledge();
             break;
         }
         default: {
@@ -421,6 +446,12 @@ void session_poll(void **data, int *len)
 {
     int l;
 
+    if((user_kernel_state == USER_KERNEL_RUNNING) && watchdog_expired()) {
+        log("Watchdog expired");
+        *len = -1;
+        return;
+    }
+
     l = get_out_packet_len();
 
     /* If the output buffer is available, 
@@ -435,7 +466,6 @@ void session_poll(void **data, int *len)
                 *len = -1;
                 return;
             }
-            mailbox_acknowledge();
         }
         l = get_out_packet_len();
     }
diff --git a/soc/targets/artiq_kc705.py b/soc/targets/artiq_kc705.py
index 43cc69fe7..ee87eb605 100644
--- a/soc/targets/artiq_kc705.py
+++ b/soc/targets/artiq_kc705.py
@@ -6,6 +6,7 @@ from mibuild.xilinx.vivado import XilinxVivadoToolchain
 
 from misoclib.com import gpio
 from misoclib.soc import mem_decoder
+from misoclib.cpu.peripherals import timer
 from targets.kc705 import MiniSoC
 
 from artiq.gateware import amp, rtio, ad9858, nist_qc1
@@ -46,7 +47,8 @@ class Top(MiniSoC):
 
     def __init__(self, platform, cpu_type="or1k", **kwargs):
         MiniSoC.__init__(self, platform,
-                         cpu_type=cpu_type, **kwargs)
+                         cpu_type=cpu_type, with_timer=False, **kwargs)
+        self.submodules.timer0 = timer.Timer(width=64)
         platform.add_extension(nist_qc1.fmc_adapter_io)
 
         self.submodules.leds = gpio.GPIOOut(Cat(
diff --git a/soc/targets/artiq_pipistrello.py b/soc/targets/artiq_pipistrello.py
index 38af077fb..531873a3d 100644
--- a/soc/targets/artiq_pipistrello.py
+++ b/soc/targets/artiq_pipistrello.py
@@ -4,6 +4,7 @@ from migen.bank import wbgen
 
 from misoclib.com import gpio
 from misoclib.soc import mem_decoder
+from misoclib.cpu.peripherals import timer
 from targets.pipistrello import BaseSoC
 
 from artiq.gateware import amp, rtio, ad9858, nist_qc1
@@ -66,7 +67,9 @@ class Top(BaseSoC):
     mem_map.update(BaseSoC.mem_map)
 
     def __init__(self, platform, cpu_type="or1k", **kwargs):
-        BaseSoC.__init__(self, platform, cpu_type=cpu_type, **kwargs)
+        BaseSoC.__init__(self, platform,
+                         cpu_type=cpu_type, with_timer=False, **kwargs)
+        self.submodules.timer0 = timer.Timer(width=64)
         platform.toolchain.ise_commands += """
 trce -v 12 -fastpaths -tsi {build_name}.tsi -o {build_name}.twr {build_name}.ncd {build_name}.pcf
 """