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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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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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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