Initial revision

c/src/lib/libbsp/m68k/idp/timer/timer.c

@@ -0,0 +1,121 @@
+/*  Timer_init()
+ *
+ *  This routine initializes the MC68230 timer on the Motorola IDP board.
+ *
+ *  Input parameters:  NONE
+ *
+ *  Output parameters:  NONE
+ *
+ *  NOTE: This routine will not work if the optimizer is enabled
+ *        for some compilers.  The multiple writes to the MC68230
+ *        may be optimized away.
+ *
+ *        It is important that the timer start/stop overhead be 
+ *        determined when porting or modifying this code.
+ *
+ *  Code Modified for the MC68230 by Doug McBride, Colorado Space Grant College
+ *
+ *  COPYRIGHT (c) 1989, 1990, 1991, 1992, 1993, 1994.
+ *  On-Line Applications Research Corporation (OAR).
+ *  All rights assigned to U.S. Government, 1994.
+ *
+ *  This material may be reproduced by or for the U.S. Government pursuant
+ *  to the copyright license under the clause at DFARS 252.227-7013.  This
+ *  notice must appear in all copies of this file and its derivatives.
+ *
+ *  $Id$
+ */
+
+
+#include "rtems.h"
+#include "cpu.h"
+#include "bsp.h"
+#include "mc68230.h"
+
+#define TIMER_VECTOR 0x4D
+
+int Ttimer_val;
+rtems_boolean Timer_driver_Find_average_overhead;
+
+rtems_isr timerisr();
+
+void Timer_initialize()
+{
+  (void) set_vector( timerisr, TIMER_VECTOR, 0 );  /* install ISR */
+  
+  Ttimer_val = 0;                          /* clear timer ISR count */
+
+  /* some PI/T initialization stuff here */
+  /* Set up the interrupt vector on the MC68230 chip:
+     TIVR = TIMER_VECTOR; */
+  MC68230_WRITE (TIVR, TIMER_VECTOR);
+
+  /* Set CPRH through CPRL to maximum count to reduce interrupt overhead
+      CPRH = 0xFF;
+      CPRM = 0xFF;
+      CPRL = 0xFF; */
+  MC68230_WRITE (CPRH, 0xFF);
+  MC68230_WRITE (CPRM, 0xFF);
+  MC68230_WRITE (CPRL, 0xFF);
+
+  /* Enable timer and use it as an external periodic interrupt generator
+      TCR = 0xA1; */
+  MC68230_WRITE (TCR, 0xA1);
+
+}
+
+#define AVG_OVERHEAD      9  /* may not be right -- do this later */
+#define LEAST_VALID       10 /* Don't trust a value lower than this */
+
+int Read_timer() 
+{
+  rtems_unsigned8 data;
+  rtems_unsigned8  msb, osb, lsb;
+  rtems_unsigned32 remaining, total;
+
+  /* Disable timer so that timer can be read
+        data = TCR;
+        TCR = (data & 0xFE); */
+  MC68230_READ (TCR, data);
+  MC68230_WRITE (TCR, (data & 0xFE));
+
+  /* Read the counter value
+        msb = CNTRH;
+        osb = CNTRM;
+        lsb = CNTRL; */
+  MC68230_READ (CNTRH, msb);
+  MC68230_READ (CNTRM, osb);
+  MC68230_READ (CNTRL, lsb);
+
+  /* Calculate the time so far */
+  remaining = 0x1000000 - ((msb << 16) + (osb << 8) + lsb);
+  total = (Ttimer_val * 0x1000000) + remaining;
+
+  /* Enable timer so that timer can continue
+	 	TCR = 0xA1; */
+  MC68230_WRITE (TCR, 0xA1);
+
+  /* do not restore old vector */
+  if ( Timer_driver_Find_average_overhead == 1 )
+    return total;          /* in countdown units */
+
+  if ( total < LEAST_VALID )
+    return 0;            /* below timer resolution */
+   
+  /* Clocked at 6.5 Mhz */
+  /* Avoid floating point problems, be lazy, and return the total minus
+     the average overhead */
+  return (total - AVG_OVERHEAD);
+}
+
+rtems_status_code Empty_function( void )
+{
+  return RTEMS_SUCCESSFUL;
+}
+
+void Set_find_average_overhead(
+  rtems_boolean find_flag
+)
+{
+  Timer_driver_Find_average_overhead = find_flag;
+}