diff --git a/py/objexcept.c b/py/objexcept.c
index cddc77bfeb5ac33b0c5e8aee6325a14b9395320d..7f9b219d561b1ad66ce1138daddda5a6fdadfbde 100644
--- a/py/objexcept.c
+++ b/py/objexcept.c
@@ -88,10 +88,10 @@ mp_obj_t mp_alloc_emergency_exception_buf(mp_obj_t size_in) {
 
     // Update the 2 variables atomically so that an interrupt can't occur
     // between the assignments.
-    MICROPY_BEGIN_ATOMIC_SECTION();
+    mp_int_t enabled = MICROPY_BEGIN_ATOMIC_SECTION();
     mp_emergency_exception_buf_size = size;
     mp_emergency_exception_buf = buf;
-    MICROPY_END_ATOMIC_SECTION();
+    MICROPY_END_ATOMIC_SECTION(enabled);
 
     if (old_buf != NULL) {
         m_free(old_buf, old_size);
diff --git a/stmhal/Makefile b/stmhal/Makefile
index 75f080587f197bb228d34bab51cc196ad841d469..ba965481a32139082e219743c6704d70b5088b11 100644
--- a/stmhal/Makefile
+++ b/stmhal/Makefile
@@ -70,6 +70,7 @@ SRC_C = \
 	usbd_desc_cdc_msc.c \
 	usbd_cdc_interface.c \
 	usbd_msc_storage.c \
+	irq.c \
 	pendsv.c \
 	systick.c  \
 	timer.c \
diff --git a/stmhal/irq.c b/stmhal/irq.c
new file mode 100644
index 0000000000000000000000000000000000000000..2d6a990beb0d0a7579c16000784ad44031a163d2
--- /dev/null
+++ b/stmhal/irq.c
@@ -0,0 +1,74 @@
+/*
+ * This file is part of the Micro Python project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2013, 2014 Damien P. George
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "mpconfig.h"
+#include "misc.h"
+#include "nlr.h"
+#include "qstr.h"
+#include "obj.h"
+#include "irq.h"
+
+#include MICROPY_HAL_H
+
+void enable_irq(mp_int_t enable) {
+  // With __set_PRIMASK 1 = disable, 0 = enable
+    __set_PRIMASK(!enable);
+}
+
+mp_int_t disable_irq(void) {
+    mp_int_t enabled = !__get_PRIMASK();
+    __disable_irq();
+    return enabled;
+}
+
+/// \function wfi()
+/// Wait for an interrupt.
+/// This executies a `wfi` instruction which reduces power consumption
+/// of the MCU until an interrupt occurs, at which point execution continues.
+STATIC mp_obj_t pyb_wfi(void) {
+    __WFI();
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_0(pyb_wfi_obj, pyb_wfi);
+
+/// \function disable_irq()
+/// Disable interrupt requests.
+STATIC mp_obj_t pyb_disable_irq(void) {
+  return MP_BOOL(disable_irq());
+}
+MP_DEFINE_CONST_FUN_OBJ_0(pyb_disable_irq_obj, pyb_disable_irq);
+
+/// \function enable_irq()
+/// Enable interrupt requests.
+STATIC mp_obj_t pyb_enable_irq(uint n_args, const mp_obj_t *arg) {
+    mp_int_t enabled = true;
+    if (n_args > 0) {
+        enabled = mp_obj_is_true(arg[0]);
+    }
+    enable_irq(enabled);
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(pyb_enable_irq_obj, 0, 1, pyb_enable_irq);
diff --git a/stmhal/irq.h b/stmhal/irq.h
new file mode 100644
index 0000000000000000000000000000000000000000..9903a02fa486aa39e1a610b9451329f395ab323d
--- /dev/null
+++ b/stmhal/irq.h
@@ -0,0 +1,36 @@
+/*
+ * This file is part of the Micro Python project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2013, 2014 Damien P. George
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+// The prototypes for disable_irq/enable_irq are in mpconfigport.h
+// Once we switch around to using traitional #include headers, then they
+// can be move back into here.
+
+// mp_int_t disable_irq(void);
+// void enable_irq(mp_int_t enabled);
+
+MP_DECLARE_CONST_FUN_OBJ(pyb_wfi_obj);
+MP_DECLARE_CONST_FUN_OBJ(pyb_disable_irq_obj);
+MP_DECLARE_CONST_FUN_OBJ(pyb_enable_irq_obj);
diff --git a/stmhal/main.c b/stmhal/main.c
index b735f49bca8e91e5d8495d231c5ad95370367983..a34ffab32507de5d042dc44ccdaf4e236589b46e 100644
--- a/stmhal/main.c
+++ b/stmhal/main.c
@@ -119,14 +119,6 @@ void MP_WEAK __assert_func(const char *file, int line, const char *func, const c
 }
 #endif
 
-void enable_irq(void) {
-    __enable_irq();
-}
-
-void disable_irq(void) {
-    __disable_irq();
-}
-
 STATIC mp_obj_t pyb_config_main = MP_OBJ_NULL;
 STATIC mp_obj_t pyb_config_usb_mode = MP_OBJ_NULL;
 
diff --git a/stmhal/modpyb.c b/stmhal/modpyb.c
index a075cf2c32bb27652224eeba6bf4fd330522b1c9..de7eac402436ac12684d393e47cacf1592a73ae7 100644
--- a/stmhal/modpyb.c
+++ b/stmhal/modpyb.c
@@ -36,6 +36,7 @@
 #include "obj.h"
 #include "gc.h"
 #include "gccollect.h"
+#include "irq.h"
 #include "systick.h"
 #include "pyexec.h"
 #include "led.h"
@@ -216,32 +217,6 @@ STATIC mp_obj_t pyb_udelay(mp_obj_t usec_in) {
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(pyb_udelay_obj, pyb_udelay);
 
-/// \function wfi()
-/// Wait for an interrupt.
-/// This executies a `wfi` instruction which reduces power consumption
-/// of the MCU until an interrupt occurs, at which point execution continues.
-STATIC mp_obj_t pyb_wfi(void) {
-    __WFI();
-    return mp_const_none;
-}
-MP_DEFINE_CONST_FUN_OBJ_0(pyb_wfi_obj, pyb_wfi);
-
-/// \function disable_irq()
-/// Disable interrupt requests.
-STATIC mp_obj_t pyb_disable_irq(void) {
-    __disable_irq();
-    return mp_const_none;
-}
-MP_DEFINE_CONST_FUN_OBJ_0(pyb_disable_irq_obj, pyb_disable_irq);
-
-/// \function enable_irq()
-/// Enable interrupt requests.
-STATIC mp_obj_t pyb_enable_irq(void) {
-    __enable_irq();
-    return mp_const_none;
-}
-MP_DEFINE_CONST_FUN_OBJ_0(pyb_enable_irq_obj, pyb_enable_irq);
-
 #if 0
 STATIC void SYSCLKConfig_STOP(void) {
     /* After wake-up from STOP reconfigure the system clock */
diff --git a/stmhal/mpconfigport.h b/stmhal/mpconfigport.h
index 5ace34ff18a1870c6d019deb7bedc417e0eae074..805d74f99656e5d7ea43c440207260de265f43c3 100644
--- a/stmhal/mpconfigport.h
+++ b/stmhal/mpconfigport.h
@@ -57,12 +57,6 @@
 #define MICROPY_ENABLE_EMERGENCY_EXCEPTION_BUF   (1)
 #define MICROPY_EMERGENCY_EXCEPTION_BUF_SIZE  (0)
 
-void enable_irq(void);
-void disable_irq(void);
-
-#define MICROPY_BEGIN_ATOMIC_SECTION()  disable_irq()
-#define MICROPY_END_ATOMIC_SECTION()    enable_irq()
-
 // extra built in names to add to the global namespace
 extern const struct _mp_obj_fun_builtin_t mp_builtin_help_obj;
 extern const struct _mp_obj_fun_builtin_t mp_builtin_input_obj;
@@ -102,6 +96,12 @@ typedef unsigned int mp_uint_t; // must be pointer size
 typedef void *machine_ptr_t; // must be of pointer size
 typedef const void *machine_const_ptr_t; // must be of pointer size
 
+mp_int_t disable_irq(void);
+void enable_irq(mp_int_t enable);
+
+#define MICROPY_BEGIN_ATOMIC_SECTION()      disable_irq()
+#define MICROPY_END_ATOMIC_SECTION(enable)  enable_irq(enable)
+
 // There is no classical C heap in bare-metal ports, only Python
 // garbage-collected heap. For completeness, emulate C heap via
 // GC heap. Note that MicroPython core never uses malloc() and friends,
diff --git a/teensy/Makefile b/teensy/Makefile
index c627f2fa6046c767a351a32ffe1c77e51c6fd871..09bee1dbcdbf227d82b0c6786ec36dfaa021d13a 100644
--- a/teensy/Makefile
+++ b/teensy/Makefile
@@ -61,6 +61,7 @@ SRC_C = \
 STM_SRC_C = $(addprefix stmhal/,\
 	gccollect.c \
 	input.c \
+	irq.c \
 	pin.c \
 	pin_named_pins.c \
 	printf.c \
diff --git a/teensy/modpyb.c b/teensy/modpyb.c
index 81149d89bffff63cbc7342a988f8b86c242cbb84..518b93be8f0d93c1b4d59d8d486f879501f3a45a 100644
--- a/teensy/modpyb.c
+++ b/teensy/modpyb.c
@@ -38,6 +38,7 @@
 #include "obj.h"
 #include "gc.h"
 #include "gccollect.h"
+#include "irq.h"
 #include "systick.h"
 #include "pyexec.h"
 #include "led.h"
@@ -181,45 +182,17 @@ STATIC mp_obj_t pyb_udelay(mp_obj_t usec_in) {
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(pyb_udelay_obj, pyb_udelay);
 
-/// \function wfi()
-/// Wait for an interrupt.
-/// This executies a `wfi` instruction which reduces power consumption
-/// of the MCU until an interrupt occurs, at which point execution continues.
-STATIC mp_obj_t pyb_wfi(void) {
-    __WFI();
-    return mp_const_none;
-}
-MP_DEFINE_CONST_FUN_OBJ_0(pyb_wfi_obj, pyb_wfi);
-
-/// \function disable_irq()
-/// Disable interrupt requests.
-STATIC mp_obj_t pyb_disable_irq(void) {
-    __disable_irq();
-    return mp_const_none;
-}
-MP_DEFINE_CONST_FUN_OBJ_0(pyb_disable_irq_obj, pyb_disable_irq);
-
-/// \function enable_irq()
-/// Enable interrupt requests.
-STATIC mp_obj_t pyb_enable_irq(void) {
-    __enable_irq();
-    return mp_const_none;
-}
-MP_DEFINE_CONST_FUN_OBJ_0(pyb_enable_irq_obj, pyb_enable_irq);
-
 STATIC mp_obj_t pyb_stop(void) {
     printf("stop not currently implemented\n");
     return mp_const_none;
 }
-
-MP_DEFINE_CONST_FUN_OBJ_0(pyb_stop_obj, pyb_stop);
+STATIC MP_DEFINE_CONST_FUN_OBJ_0(pyb_stop_obj, pyb_stop);
 
 STATIC mp_obj_t pyb_standby(void) {
     printf("standby not currently implemented\n");
     return mp_const_none;
 }
-
-MP_DEFINE_CONST_FUN_OBJ_0(pyb_standby_obj, pyb_standby);
+STATIC MP_DEFINE_CONST_FUN_OBJ_0(pyb_standby_obj, pyb_standby);
 
 /// \function have_cdc()
 /// Return True if USB is connected as a serial device, False otherwise.
diff --git a/teensy/mpconfigport.h b/teensy/mpconfigport.h
index 697106378e1e01170550d2426f8a0c20526becbb..ec68c9b5bc65c9bf3225c9a660438b6bd4603965 100644
--- a/teensy/mpconfigport.h
+++ b/teensy/mpconfigport.h
@@ -51,6 +51,12 @@ typedef unsigned int mp_uint_t; // must be pointer size
 typedef void *machine_ptr_t; // must be of pointer size
 typedef const void *machine_const_ptr_t; // must be of pointer size
 
+mp_int_t disable_irq(void);
+void enable_irq(mp_int_t enable);
+
+#define MICROPY_BEGIN_ATOMIC_SECTION()      disable_irq()
+#define MICROPY_END_ATOMIC_SECTION(enable)  enable_irq(enable)
+
 // There is no classical C heap in bare-metal ports, only Python
 // garbage-collected heap. For completeness, emulate C heap via
 // GC heap. Note that MicroPython core never uses malloc() and friends,
diff --git a/teensy/teensy_hal.h b/teensy/teensy_hal.h
index 9c9e628424cd93d71c96d1d794b7a9764a39aecc..ffbb70bcc393602d671b2e43cafcfc48b67f2497 100644
--- a/teensy/teensy_hal.h
+++ b/teensy/teensy_hal.h
@@ -1,3 +1,4 @@
+#include <mk20dx128.h>
 
 #ifdef  USE_FULL_ASSERT
   #define assert_param(expr) ((expr) ? (void)0 : assert_failed((uint8_t *)__FILE__, __LINE__))
@@ -118,6 +119,19 @@ __attribute__(( always_inline )) static inline void __WFI(void)
   __asm volatile ("wfi");
 }
 
+__attribute__(( always_inline )) static inline uint32_t __get_PRIMASK(void)
+{
+    uint32_t result;
+    __asm volatile ("MRS %0, primask" : "=r" (result));
+    return(result);
+}
+
+__attribute__(( always_inline )) static inline void __set_PRIMASK(uint32_t priMask)
+{
+    __asm volatile ("MSR primask, %0" : : "r" (priMask) : "memory");
+}
+
+
 uint32_t HAL_GetTick(void);
 void     HAL_Delay(uint32_t Delay);