Merge devel code into the trunk.

[tinyos-2.x.git] / tos / platforms / mica / BusyWaitMicroC.nc

diff --git a/tos/platforms/mica/BusyWaitMicroC.nc b/tos/platforms/mica/BusyWaitMicroC.nc
new file mode 100644 (file)
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+/*                                                                     tab:4
+ * "Copyright (c) 2000-2003 The Regents of the University  of California.  
+ * All rights reserved.
+ *
+ * Permission to use, copy, modify, and distribute this software and its
+ * documentation for any purpose, without fee, and without written agreement is
+ * hereby granted, provided that the above copyright notice, the following
+ * two paragraphs and the author appear in all copies of this software.
+ * 
+ * IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY FOR
+ * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT
+ * OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF THE UNIVERSITY OF
+ * CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ * 
+ * THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
+ * ON AN "AS IS" BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATION TO
+ * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS."
+ *
+ * Copyright (c) 2002-2006 Intel Corporation
+ * All rights reserved.
+ *
+ * This file is distributed under the terms in the attached INTEL-LICENSE     
+ * file. If you do not find these files, copies can be found by writing to
+ * Intel Research Berkeley, 2150 Shattuck Avenue, Suite 1300, Berkeley, CA, 
+ * 94704.  Attention:  Intel License Inquiry.
+ */
+/**
+ * Busy wait component as per TEP102. Supports waiting for at least some
+ * number of microseconds. This functionality should be used sparingly,
+ * when the overhead of posting a Timer or Alarm is greater than simply
+ * busy waiting.
+ *
+ * @author David Gay
+ */
+
+module BusyWaitMicroC
+{
+  provides interface BusyWait<TMicro,uint16_t>;
+}
+implementation
+{
+  inline async command void BusyWait.wait(uint16_t dt) {
+  /* In most cases (constant arg), the test is elided at compile-time */
+  if (dt)
+#if MHZ == 1
+    {
+      dt = (dt + 3) >> 2;
+    /* loop takes 4 cycles. */
+      asm volatile (
+"1:    sbiw    %0,1\n"
+"      brne    1b" : "+w" (dt));
+    }
+#elif MHZ == 2
+    {
+      dt = (dt + 1) >> 1;
+    /* loop takes 4 cycles. */
+      asm volatile (
+"1:    sbiw    %0,1\n"
+"      brne    1b" : "+w" (dt));
+    }
+#elif MHZ == 4
+    /* loop takes 4 cycles. */
+    asm volatile (
+"1:    sbiw    %0,1\n"
+"      brne    1b" : "+w" (dt));
+#elif MHZ == 8
+    /* loop takes 8 cycles. this is 1uS if running on an internal 8MHz
+       clock, and 1.09uS if running on the external crystal. */
+    asm volatile (
+"1:    sbiw    %0,1\n"
+"      adiw    %0,1\n"
+"      sbiw    %0,1\n"
+"      brne    1b" : "+w" (dt));
+#else
+#error "Unknown clock rate. MHZ must be defined to one of 1, 2, 4, or 8."
+#endif
+  }
+}