1 files changed, 60 insertions, 0 deletions
diff --git a/time/system_tick.S b/time/system_tick.S
new file mode 100644
index 0000000..c1f90fd
--- /dev/null
+++ b/time/system_tick.S
@@ -0,0 +1,60 @@
+/*
+ * (c)2012 Michael Duane Rice All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ * Redistributions of source code must retain the above copyright notice, this
+ * list of conditions and the following disclaimer. Redistributions in binary
+ * form must reproduce the above copyright notice, this list of conditions
+ * and the following disclaimer in the documentation and/or other materials
+ * provided with the distribution. Neither the name of the copyright holders
+ * nor the names of contributors may be used to endorse or promote products
+ * derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/* $Id: system_tick.S 2348 2013-04-16 23:42:05Z swfltek $ */
+
+/*
+    Impoved system_tick Credit to Wouter van Gulik.
+*/
+
+#include <avr/common.h>
+
+    .global	system_tick
+	.type	system_tick, @function
+system_tick:
+    push r24
+    in r24,_SFR_IO_ADDR(SREG)
+	push r24
+	cli
+    lds r24,__system_time+0
+    subi r24, (-1)
+    sts __system_time+0,r24
+    lds r24,__system_time+1
+    sbci r24, (-1)
+    sts __system_time+1,r24
+    lds r24,__system_time+2
+    sbci r24, (-1)
+    sts __system_time+2,r24
+    lds r24,__system_time+3
+    sbci r24, (-1)
+    sts __system_time+3,r24
+    pop r24
+    out _SFR_IO_ADDR(SREG),r24
+    pop r24
+    ret
+	.size	system_tick, .-system_tick