[0074691a] | 1 | /* Timer_init() |
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| 2 | * |
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| 3 | * This routine initializes TIMER 2 for an MC68302. |
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| 4 | * |
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| 5 | * Input parameters: NONE |
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| 6 | * |
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| 7 | * Output parameters: NONE |
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| 8 | * |
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| 9 | * NOTE: It is important that the timer start/stop overhead be |
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| 10 | * determined when porting or modifying this code. |
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| 11 | * |
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| 12 | * COPYRIGHT (c) 1989-1997. |
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| 13 | * On-Line Applications Research Corporation (OAR). |
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| 14 | * Copyright assigned to U.S. Government, 1994. |
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| 15 | * |
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[98e4ebf5] | 16 | * The license and distribution terms for this file may be |
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| 17 | * found in the file LICENSE in this distribution or at |
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[0074691a] | 18 | * http://www.OARcorp.com/rtems/license.html. |
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| 19 | * |
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| 20 | * $Id$ |
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| 21 | */ |
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| 22 | |
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| 23 | |
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| 24 | #include <rtems.h> |
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| 25 | #include <bsp.h> |
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| 26 | #include "m68302.h" |
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| 27 | |
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| 28 | |
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| 29 | #define TMR2_VAL 0x071b /* Timer mode register |
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| 30 | * (section 3.5.2.1 in 68302 manual) |
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| 31 | * 15-8: "7" prescaler divide by 8 (x+1) |
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| 32 | * 7-6: 00 dis. intr. on capture event |
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| 33 | * 5: 0 active-low pulse |
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| 34 | * 4: 1 intr. on reaching reference |
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| 35 | * 3: 1 restart counter on reference |
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| 36 | * 2-1: 01 master clock input source |
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| 37 | * 0: 1 enable timer |
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| 38 | */ |
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| 39 | #define TRR2_VAL 2000 /* Timer reference register |
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| 40 | * (section 3.5.2.2 in 68302 manual) |
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| 41 | * 2000 ticks @ (16MHz/1)/8 = 1-ms count |
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| 42 | */ |
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| 43 | |
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| 44 | rtems_unsigned32 Timer_interrupts; |
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| 45 | |
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| 46 | rtems_boolean Timer_driver_Find_average_overhead; |
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| 47 | |
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| 48 | rtems_isr timerisr(); |
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| 49 | |
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| 50 | void Timer_initialize( void ) |
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| 51 | { |
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| 52 | m302.reg.tmr2 = 0; /* disable timer */ |
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| 53 | |
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| 54 | Timer_interrupts = 0; /* clear timer ISR count */ |
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| 55 | |
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| 56 | m302.reg.trr2 = TRR2_VAL; /* set timer reference register */ |
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| 57 | m302.reg.tmr2 = TMR2_VAL; /* set timer mode register */ |
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| 58 | m302.reg.imr |= RBIT_IMR_TIMER2; /* set 68302 int-mask to allow ints */ |
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| 59 | } |
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| 60 | |
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| 61 | /* |
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| 62 | * The following controls the behavior of Read_timer(). |
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| 63 | * |
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| 64 | * FIND_AVG_OVERHEAD * instructs the routine to return the "raw" count. |
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| 65 | * |
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| 66 | * AVG_OVEREHAD is the overhead for starting and stopping the timer. It |
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| 67 | * is usually deducted from the number returned. |
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| 68 | * |
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| 69 | * LEAST_VALID is the lowest number this routine should trust. Numbers |
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| 70 | * below this are "noise" and zero is returned. |
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| 71 | */ |
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| 72 | |
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| 73 | #define AVG_OVERHEAD 0 /* It typically takes X.X microseconds */ |
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| 74 | /* (Y countdowns) to start/stop the timer. */ |
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| 75 | /* This value is in microseconds. */ |
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| 76 | #define LEAST_VALID 1 /* Don't trust a clicks value lower than this */ |
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| 77 | |
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| 78 | /* |
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| 79 | * Return timer value in 1/2-microsecond units |
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| 80 | */ |
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| 81 | int Read_timer( void ) |
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| 82 | { |
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| 83 | rtems_unsigned16 clicks; |
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| 84 | rtems_unsigned32 total; |
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| 85 | |
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| 86 | /* |
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| 87 | * Read the timer and see how many clicks it has been since counter |
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| 88 | * rolled over. |
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| 89 | */ |
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| 90 | |
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| 91 | clicks = m302.reg.tcn2; |
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| 92 | |
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| 93 | /* |
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| 94 | * Total is calculated by taking into account the number of timer overflow |
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| 95 | * interrupts since the timer was initialized and clicks since the last |
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| 96 | * interrupts. |
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| 97 | */ |
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| 98 | |
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| 99 | total = (Timer_interrupts * TRR2_VAL) + clicks; |
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| 100 | |
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| 101 | if ( Timer_driver_Find_average_overhead == 1 ) |
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| 102 | return total; /* in XXX microsecond units */ |
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| 103 | |
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| 104 | if ( total < LEAST_VALID ) |
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| 105 | return 0; /* below timer resolution */ |
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| 106 | |
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| 107 | /* |
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| 108 | * Convert 1/2-microsecond count into microseconds |
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| 109 | */ |
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| 110 | |
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| 111 | return (total - AVG_OVERHEAD) >> 1; |
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| 112 | } |
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| 113 | |
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| 114 | |
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| 115 | /* |
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| 116 | * Empty function call used in loops to measure basic cost of looping |
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| 117 | * in Timing Test Suite. |
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| 118 | */ |
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| 119 | |
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| 120 | rtems_status_code Empty_function(void) |
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| 121 | { |
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| 122 | return RTEMS_SUCCESSFUL; |
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| 123 | } |
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| 124 | |
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| 125 | void Set_find_average_overhead( |
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| 126 | rtems_boolean find_flag |
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| 127 | ) |
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| 128 | { |
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| 129 | Timer_driver_Find_average_overhead = find_flag; |
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| 130 | } |
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