1 | @c |
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2 | @c COPYRIGHT (c) 1988-2008 |
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3 | @c On-Line Applications Research Corporation (OAR). |
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4 | @c All rights reserved. |
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5 | @c |
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6 | @c $Id$ |
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7 | @c |
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8 | |
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9 | @chapter Clock Manager |
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10 | |
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11 | @cindex clock |
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12 | |
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13 | @section Introduction |
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14 | |
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15 | The clock manager provides support for time of day |
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16 | and other time related capabilities. The directives provided by |
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17 | the clock manager are: |
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18 | |
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19 | @itemize @bullet |
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20 | @item @code{@value{DIRPREFIX}clock_set} - Set date and time |
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21 | @item @code{@value{DIRPREFIX}clock_get} - Get date and time information |
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22 | @item @code{@value{DIRPREFIX}clock_get_tod} - Get date and time in TOD format |
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23 | @item @code{@value{DIRPREFIX}clock_get_tod_timeval} - Get date and time in timeval format |
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24 | @item @code{@value{DIRPREFIX}clock_get_seconds_since_epoch} - Get seconds since epoch |
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25 | @item @code{@value{DIRPREFIX}clock_get_ticks_per_second} - Get ticks per second |
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26 | @item @code{@value{DIRPREFIX}clock_get_ticks_since_boot} - Get ticks since boot |
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27 | @item @code{@value{DIRPREFIX}clock_get_uptime} - Get time since boot |
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28 | @item @code{@value{DIRPREFIX}clock_set_nanoseconds_extension} - Install the nanoseconds since last tick handler |
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29 | @item @code{@value{DIRPREFIX}clock_tick} - Announce a clock tick |
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30 | @end itemize |
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31 | |
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32 | @section Background |
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33 | |
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34 | @subsection Required Support |
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35 | |
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36 | For the features provided by the clock manager to be |
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37 | utilized, periodic timer interrupts are required. Therefore, a |
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38 | real-time clock or hardware timer is necessary to create the |
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39 | timer interrupts. The @code{@value{DIRPREFIX}clock_tick} |
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40 | directive is normally called |
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41 | by the timer ISR to announce to RTEMS that a system clock tick |
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42 | has occurred. Elapsed time is measured in ticks. A tick is |
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43 | defined to be an integral number of microseconds which is |
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44 | specified by the user in the Configuration Table. |
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45 | |
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46 | @subsection Time and Date Data Structures |
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47 | |
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48 | The clock facilities of the clock manager operate |
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49 | upon calendar time. These directives utilize the following date |
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50 | and time @value{STRUCTURE} for the native time and date format: |
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51 | |
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52 | |
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53 | @ifset is-C |
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54 | @findex rtems_time_of_day |
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55 | @example |
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56 | struct rtems_tod_control @{ |
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57 | uint32_t year; /* greater than 1987 */ |
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58 | uint32_t month; /* 1 - 12 */ |
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59 | uint32_t day; /* 1 - 31 */ |
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60 | uint32_t hour; /* 0 - 23 */ |
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61 | uint32_t minute; /* 0 - 59 */ |
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62 | uint32_t second; /* 0 - 59 */ |
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63 | uint32_t ticks; /* elapsed between seconds */ |
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64 | @}; |
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65 | |
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66 | typedef struct rtems_tod_control rtems_time_of_day; |
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67 | @end example |
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68 | @end ifset |
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69 | |
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70 | @ifset is-Ada |
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71 | @example |
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72 | type Time_Of_Day is |
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73 | record |
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74 | Year : RTEMS.Unsigned32; -- year, A.D. |
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75 | Month : RTEMS.Unsigned32; -- month, 1 .. 12 |
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76 | Day : RTEMS.Unsigned32; -- day, 1 .. 31 |
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77 | Hour : RTEMS.Unsigned32; -- hour, 0 .. 23 |
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78 | Minute : RTEMS.Unsigned32; -- minute, 0 .. 59 |
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79 | Second : RTEMS.Unsigned32; -- second, 0 .. 59 |
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80 | Ticks : RTEMS.Unsigned32; -- elapsed ticks between seconds |
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81 | end record; |
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82 | @end example |
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83 | @end ifset |
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84 | |
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85 | |
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86 | The native date and time format is the only format |
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87 | supported when setting the system date and time using the |
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88 | @code{@value{DIRPREFIX}clock_get} directive. Some applications |
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89 | expect to operate on a "UNIX-style" date and time data structure. The |
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90 | @code{@value{DIRPREFIX}clock_get} directive can optionally return |
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91 | the current date and time in the |
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92 | following @value{STRUCTURE}: |
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93 | |
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94 | @ifset is-C |
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95 | @example |
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96 | @group |
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97 | typedef struct @{ |
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98 | uint32_t seconds; /* seconds since RTEMS epoch*/ |
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99 | uint32_t microseconds; /* since last second */ |
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100 | @} rtems_clock_time_value; |
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101 | @end group |
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102 | @end example |
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103 | @end ifset |
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104 | |
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105 | @ifset is-Ada |
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106 | @example |
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107 | type Clock_Time_Value is |
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108 | record |
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109 | Seconds : Unsigned32; |
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110 | Microseconds : Unsigned32; |
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111 | end record; |
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112 | @end example |
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113 | @end ifset |
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114 | |
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115 | The seconds field in this @value{STRUCTURE} is the number of seconds |
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116 | since the POSIX epoch of January 1, 1970 but will never be prior to |
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117 | the RTEMS epoch of January 1, 1988. |
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118 | |
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119 | @subsection Clock Tick and Timeslicing |
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120 | |
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121 | @cindex timeslicing |
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122 | |
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123 | Timeslicing is a task scheduling discipline in which |
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124 | tasks of equal priority are executed for a specific period of |
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125 | time before control of the CPU is passed to another task. It is |
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126 | also sometimes referred to as the automatic round-robin |
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127 | scheduling algorithm. The length of time allocated to each task |
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128 | is known as the quantum or timeslice. |
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129 | |
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130 | The system's timeslice is defined as an integral |
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131 | number of ticks, and is specified in the Configuration Table. |
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132 | The timeslice is defined for the entire system of tasks, but |
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133 | timeslicing is enabled and disabled on a per task basis. |
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134 | |
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135 | The @code{@value{DIRPREFIX}clock_tick} |
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136 | directive implements timeslicing by |
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137 | decrementing the running task's time-remaining counter when both |
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138 | timeslicing and preemption are enabled. If the task's timeslice |
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139 | has expired, then that task will be preempted if there exists a |
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140 | ready task of equal priority. |
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141 | |
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142 | @subsection Delays |
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143 | |
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144 | @cindex delays |
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145 | |
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146 | A sleep timer allows a task to delay for a given |
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147 | interval or up until a given time, and then wake and continue |
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148 | execution. This type of timer is created automatically by the |
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149 | @code{@value{DIRPREFIX}task_wake_after} |
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150 | and @code{@value{DIRPREFIX}task_wake_when} directives and, as a result, |
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151 | does not have an RTEMS ID. Once activated, a sleep timer cannot |
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152 | be explicitly deleted. Each task may activate one and only one |
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153 | sleep timer at a time. |
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154 | |
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155 | @subsection Timeouts |
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156 | |
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157 | @cindex timeouts |
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158 | |
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159 | Timeouts are a special type of timer automatically |
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160 | created when the timeout option is used on the |
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161 | @code{@value{DIRPREFIX}message_queue_receive}, |
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162 | @code{@value{DIRPREFIX}event_receive}, |
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163 | @code{@value{DIRPREFIX}semaphore_obtain} and |
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164 | @code{@value{DIRPREFIX}region_get_segment} directives. |
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165 | Each task may have one and only one timeout active at a time. |
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166 | When a timeout expires, it unblocks the task with a timeout status code. |
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167 | |
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168 | @section Operations |
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169 | |
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170 | @subsection Announcing a Tick |
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171 | |
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172 | RTEMS provides the @code{@value{DIRPREFIX}clock_tick} directive which is |
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173 | called from the user's real-time clock ISR to inform RTEMS that |
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174 | a tick has elapsed. The tick frequency value, defined in |
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175 | microseconds, is a configuration parameter found in the |
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176 | Configuration Table. RTEMS divides one million microseconds |
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177 | (one second) by the number of microseconds per tick to determine |
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178 | the number of calls to the |
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179 | @code{@value{DIRPREFIX}clock_tick} directive per second. The |
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180 | frequency of @code{@value{DIRPREFIX}clock_tick} |
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181 | calls determines the resolution |
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182 | (granularity) for all time dependent RTEMS actions. For |
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183 | example, calling @code{@value{DIRPREFIX}clock_tick} |
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184 | ten times per second yields a higher |
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185 | resolution than calling @code{@value{DIRPREFIX}clock_tick} |
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186 | two times per second. The @code{@value{DIRPREFIX}clock_tick} |
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187 | directive is responsible for maintaining both |
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188 | calendar time and the dynamic set of timers. |
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189 | |
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190 | @subsection Setting the Time |
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191 | |
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192 | The @code{@value{DIRPREFIX}clock_set} directive allows a task or an ISR to |
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193 | set the date and time maintained by RTEMS. If setting the date |
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194 | and time causes any outstanding timers to pass their deadline, |
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195 | then the expired timers will be fired during the invocation of |
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196 | the @code{@value{DIRPREFIX}clock_set} directive. |
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197 | |
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198 | @subsection Obtaining the Time |
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199 | |
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200 | The @code{@value{DIRPREFIX}clock_get} directive allows a task or an ISR to |
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201 | obtain the current date and time or date and time related |
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202 | information. The current date and time can be returned in |
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203 | either native or UNIX-style format. Additionally, the |
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204 | application can obtain date and time related information such as |
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205 | the number of seconds since the RTEMS epoch, the number of ticks |
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206 | since the executive was initialized, and the number of ticks per |
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207 | second. The information returned by the |
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208 | @code{@value{DIRPREFIX}clock_get} directive is |
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209 | dependent on the option selected by the caller. This |
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210 | is specified using one of the following constants |
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211 | associated with the enumerated type |
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212 | @code{@value{DIRPREFIX}clock_get_options}: |
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213 | |
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214 | @findex rtems_clock_get_options |
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215 | |
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216 | @itemize @bullet |
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217 | @item @code{@value{RPREFIX}CLOCK_GET_TOD} - obtain native style date and time |
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218 | |
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219 | @item @code{@value{RPREFIX}CLOCK_GET_TIME_VALUE} - obtain UNIX-style |
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220 | date and time |
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221 | |
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222 | @item @code{@value{RPREFIX}CLOCK_GET_TICKS_SINCE_BOOT} - obtain number of ticks |
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223 | since RTEMS was initialized |
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224 | |
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225 | @item @code{@value{RPREFIX}CLOCK_GET_SECONDS_SINCE_EPOCH} - obtain number |
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226 | of seconds since RTEMS epoch |
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227 | |
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228 | @item @code{@value{RPREFIX}CLOCK_GET_TICKS_PER_SECOND} - obtain number of clock |
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229 | ticks per second |
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230 | |
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231 | @end itemize |
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232 | |
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233 | Calendar time operations will return an error code if |
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234 | invoked before the date and time have been set. |
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235 | |
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236 | @section Directives |
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237 | |
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238 | This section details the clock manager's directives. |
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239 | A subsection is dedicated to each of this manager's directives |
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240 | and describes the calling sequence, related constants, usage, |
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241 | and status codes. |
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242 | |
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243 | @c |
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244 | @c |
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245 | @c |
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246 | @page |
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247 | @subsection CLOCK_SET - Set date and time |
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248 | |
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249 | @subheading CALLING SEQUENCE: |
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250 | |
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251 | @cindex set the time of day |
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252 | |
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253 | @ifset is-C |
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254 | @findex rtems_clock_set |
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255 | @example |
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256 | rtems_status_code rtems_clock_set( |
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257 | rtems_time_of_day *time_buffer |
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258 | ); |
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259 | @end example |
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260 | @end ifset |
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261 | |
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262 | @ifset is-Ada |
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263 | @example |
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264 | procedure Clock_Set ( |
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265 | Time_Buffer : in RTEMS.Time_Of_Day; |
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266 | Result : out RTEMS.Status_Codes |
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267 | ); |
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268 | @end example |
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269 | @end ifset |
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270 | |
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271 | @subheading DIRECTIVE STATUS CODES: |
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272 | @code{@value{RPREFIX}SUCCESSFUL} - date and time set successfully@* |
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273 | @code{@value{RPREFIX}INVALID_ADDRESS} - @code{time_buffer} is NULL@* |
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274 | @code{@value{RPREFIX}INVALID_CLOCK} - invalid time of day |
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275 | |
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276 | @subheading DESCRIPTION: |
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277 | |
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278 | This directive sets the system date and time. The |
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279 | date, time, and ticks in the time_buffer @value{STRUCTURE} are all |
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280 | range-checked, and an error is returned if any one is out of its |
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281 | valid range. |
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282 | |
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283 | @subheading NOTES: |
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284 | |
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285 | Years before 1988 are invalid. |
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286 | |
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287 | The system date and time are based on the configured |
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288 | tick rate (number of microseconds in a tick). |
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289 | |
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290 | Setting the time forward may cause a higher priority |
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291 | task, blocked waiting on a specific time, to be made ready. In |
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292 | this case, the calling task will be preempted after the next |
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293 | clock tick. |
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294 | |
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295 | Re-initializing RTEMS causes the system date and time |
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296 | to be reset to an uninitialized state. Another call to |
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297 | @code{@value{DIRPREFIX}clock_set} is required to re-initialize |
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298 | the system date and time to application specific specifications. |
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299 | |
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300 | @c |
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301 | @c |
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302 | @c |
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303 | @page |
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304 | @subsection CLOCK_GET - Get date and time information |
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305 | |
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306 | @cindex obtain the time of day |
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307 | |
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308 | @subheading CALLING SEQUENCE: |
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309 | |
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310 | @ifset is-C |
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311 | @findex rtems_clock_get |
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312 | @example |
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313 | rtems_status_code rtems_clock_get( |
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314 | rtems_clock_get_options option, |
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315 | void *time_buffer |
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316 | ); |
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317 | @end example |
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318 | @end ifset |
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319 | |
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320 | @ifset is-Ada |
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321 | @example |
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322 | procedure Clock_Get ( |
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323 | Option : in RTEMS.Clock_Get_Options; |
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324 | Time_Buffer : in RTEMS.Address; |
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325 | Result : out RTEMS.Status_Codes |
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326 | ); |
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327 | @end example |
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328 | @end ifset |
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329 | |
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330 | @subheading DIRECTIVE STATUS CODES: |
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331 | @code{@value{RPREFIX}SUCCESSFUL} - current time obtained successfully@* |
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332 | @code{@value{RPREFIX}NOT_DEFINED} - system date and time is not set@* |
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333 | @code{@value{RPREFIX}INVALID_ADDRESS} - @code{time_buffer} is NULL |
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334 | |
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335 | @subheading DESCRIPTION: |
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336 | |
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337 | This directive obtains the system date and time. If |
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338 | the caller is attempting to obtain the date and time (i.e. |
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339 | option is set to either @code{@value{RPREFIX}CLOCK_GET_SECONDS_SINCE_EPOCH}, |
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340 | @code{@value{RPREFIX}CLOCK_GET_TOD}, or |
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341 | @code{@value{RPREFIX}CLOCK_GET_TIME_VALUE}) and the date and time |
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342 | has not been set with a previous call to |
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343 | @code{@value{DIRPREFIX}clock_set}, then the |
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344 | @code{@value{RPREFIX}NOT_DEFINED} status code is returned. |
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345 | The caller can always obtain the number of ticks per second (option is |
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346 | @code{@value{RPREFIX}CLOCK_GET_TICKS_PER_SECOND}) and the number of |
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347 | ticks since the executive was initialized option is |
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348 | @code{@value{RPREFIX}CLOCK_GET_TICKS_SINCE_BOOT}). |
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349 | |
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350 | The @code{option} argument may taken on any value of the enumerated |
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351 | type @code{rtems_clock_get_options}. The data type expected for |
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352 | @code{time_buffer} is based on the value of @code{option} as |
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353 | indicated below: |
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354 | |
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355 | @findex rtems_clock_get_options |
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356 | @ifset is-C |
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357 | @itemize @bullet |
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358 | @item @code{@value{RPREFIX}CLOCK_GET_TOD} - (rtems_time_of_day *) |
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359 | |
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360 | @item @code{@value{RPREFIX}CLOCK_GET_SECONDS_SINCE_EPOCH} - (rtems_interval *) |
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361 | |
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362 | @item @code{@value{RPREFIX}CLOCK_GET_TICKS_SINCE_BOOT} - (rtems_interval *) |
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363 | |
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364 | @item @code{@value{RPREFIX}CLOCK_GET_TICKS_PER_SECOND} - (rtems_interval *) |
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365 | |
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366 | @item @code{@value{RPREFIX}CLOCK_GET_TIME_VALUE} - (rtems_clock_time_value *) |
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367 | |
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368 | @end itemize |
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369 | @end ifset |
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370 | |
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371 | @ifset is-Ada |
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372 | @itemize @bullet |
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373 | @item @code{@value{RPREFIX}Clock_Get_TOD} - Address of an variable of |
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374 | type RTEMS.Time_Of_Day |
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375 | |
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376 | @item @code{@value{RPREFIX}Clock_Get_Seconds_Since_Epoch} - Address of an |
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377 | variable of type RTEMS.Interval |
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378 | |
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379 | @item @code{@value{RPREFIX}Clock_Get_Ticks_Since_Boot} - Address of an |
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380 | variable of type RTEMS.Interval |
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381 | |
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382 | @item @code{@value{RPREFIX}Clock_Get_Ticks_Per_Second} - Address of an |
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383 | variable of type RTEMS.Interval |
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384 | |
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385 | @item @code{@value{RPREFIX}Clock_Get_Time_Value} - Address of an variable of |
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386 | type RTEMS.Clock_Time_Value |
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387 | |
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388 | @end itemize |
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389 | @end ifset |
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390 | |
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391 | @subheading NOTES: |
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392 | |
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393 | This directive is callable from an ISR. |
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394 | |
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395 | This directive will not cause the running task to be |
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396 | preempted. Re-initializing RTEMS causes the system date and |
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397 | time to be reset to an uninitialized state. Another call to |
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398 | @code{@value{DIRPREFIX}clock_set} is required to re-initialize the |
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399 | system date and time to application specific specifications. |
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400 | |
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401 | @c |
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402 | @c |
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403 | @c |
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404 | @page |
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405 | @subsection CLOCK_GET_TOD - Get date and time in TOD format |
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406 | |
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407 | @cindex obtain the time of day |
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408 | |
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409 | @subheading CALLING SEQUENCE: |
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410 | |
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411 | @ifset is-C |
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412 | @findex rtems_clock_get_tod |
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413 | @example |
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414 | rtems_status_code rtems_clock_get_tod( |
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415 | rtems_time_of_day *time_buffer |
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416 | ); |
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417 | @end example |
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418 | @end ifset |
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419 | |
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420 | @ifset is-Ada |
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421 | @example |
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422 | procedure Clock_Get_TOD ( |
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423 | Time_Buffer : in RTEMS.Time_Of_Day; |
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424 | Result : out RTEMS.Status_Codes |
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425 | ); |
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426 | @end example |
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427 | @end ifset |
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428 | |
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429 | @subheading DIRECTIVE STATUS CODES: |
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430 | @code{@value{RPREFIX}SUCCESSFUL} - current time obtained successfully@* |
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431 | @code{@value{RPREFIX}NOT_DEFINED} - system date and time is not set@* |
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432 | @code{@value{RPREFIX}INVALID_ADDRESS} - @code{time_buffer} is NULL |
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433 | |
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434 | @subheading DESCRIPTION: |
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435 | |
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436 | This directive obtains the system date and time. If the date and time |
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437 | has not been set with a previous call to |
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438 | @code{@value{DIRPREFIX}clock_set}, then the |
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439 | @code{@value{RPREFIX}NOT_DEFINED} status code is returned. |
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440 | |
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441 | @subheading NOTES: |
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442 | |
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443 | This directive is callable from an ISR. |
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444 | |
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445 | This directive will not cause the running task to be |
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446 | preempted. Re-initializing RTEMS causes the system date and |
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447 | time to be reset to an uninitialized state. Another call to |
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448 | @code{@value{DIRPREFIX}clock_set} is required to re-initialize the |
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449 | system date and time to application specific specifications. |
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450 | |
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451 | @c |
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452 | @c |
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453 | @c |
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454 | @page |
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455 | @subsection CLOCK_GET_TOD_TIMEVAL - Get date and time in timeval format |
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456 | |
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457 | @cindex obtain the time of day |
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458 | |
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459 | @subheading CALLING SEQUENCE: |
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460 | |
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461 | @ifset is-C |
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462 | @findex rtems_clock_get_tod_timeval |
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463 | @example |
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464 | rtems_status_code rtems_clock_get_tod( |
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465 | struct timeval *time |
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466 | ); |
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467 | @end example |
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468 | @end ifset |
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469 | |
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470 | @ifset is-Ada |
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471 | @example |
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472 | procedure Clock_Get_TOD_Timeval ( |
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473 | Time : in RTEMS.Timeval; |
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474 | Result : out RTEMS.Status_Codes |
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475 | ); |
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476 | @end example |
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477 | @end ifset |
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478 | |
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479 | @subheading DIRECTIVE STATUS CODES: |
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480 | @code{@value{RPREFIX}SUCCESSFUL} - current time obtained successfully@* |
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481 | @code{@value{RPREFIX}NOT_DEFINED} - system date and time is not set@* |
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482 | @code{@value{RPREFIX}INVALID_ADDRESS} - @code{time} is NULL |
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483 | |
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484 | @subheading DESCRIPTION: |
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485 | |
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486 | This directive obtains the system date and time in POSIX |
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487 | @code{struct timeval} format. If the date and time |
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488 | has not been set with a previous call to |
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489 | @code{@value{DIRPREFIX}clock_set}, then the |
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490 | @code{@value{RPREFIX}NOT_DEFINED} status code is returned. |
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491 | |
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492 | @subheading NOTES: |
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493 | |
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494 | This directive is callable from an ISR. |
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495 | |
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496 | This directive will not cause the running task to be |
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497 | preempted. Re-initializing RTEMS causes the system date and |
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498 | time to be reset to an uninitialized state. Another call to |
---|
499 | @code{@value{DIRPREFIX}clock_set} is required to re-initialize the |
---|
500 | system date and time to application specific specifications. |
---|
501 | |
---|
502 | @c |
---|
503 | @c |
---|
504 | @c |
---|
505 | @page |
---|
506 | @subsection CLOCK_GET_SECONDS_SINCE_EPOCH - Get seconds since epoch |
---|
507 | |
---|
508 | @cindex obtain seconds since epoch |
---|
509 | |
---|
510 | @subheading CALLING SEQUENCE: |
---|
511 | |
---|
512 | @ifset is-C |
---|
513 | @findex rtems_clock_get_seconds_since_epoch |
---|
514 | @example |
---|
515 | rtems_status_code rtems_clock_get_seconds_since_epoch( |
---|
516 | rtems_interval *the_interval |
---|
517 | ); |
---|
518 | @end example |
---|
519 | @end ifset |
---|
520 | |
---|
521 | @ifset is-Ada |
---|
522 | @example |
---|
523 | procedure Clock_Get_Seconds_Since_Epoch( |
---|
524 | The_Interval : out RTEMS.Interval; |
---|
525 | Result : out RTEMS.Status_Codes |
---|
526 | ); |
---|
527 | @end example |
---|
528 | @end ifset |
---|
529 | |
---|
530 | @subheading DIRECTIVE STATUS CODES: |
---|
531 | @code{@value{RPREFIX}SUCCESSFUL} - current time obtained successfully@* |
---|
532 | @code{@value{RPREFIX}NOT_DEFINED} - system date and time is not set@* |
---|
533 | @code{@value{RPREFIX}INVALID_ADDRESS} - @code{the_interval} is NULL |
---|
534 | |
---|
535 | @subheading DESCRIPTION: |
---|
536 | |
---|
537 | This directive returns the number of seconds since the RTEMS |
---|
538 | epoch and the current system date and time. If the date and time |
---|
539 | has not been set with a previous call to |
---|
540 | @code{@value{DIRPREFIX}clock_set}, then the |
---|
541 | @code{@value{RPREFIX}NOT_DEFINED} status code is returned. |
---|
542 | |
---|
543 | @subheading NOTES: |
---|
544 | |
---|
545 | This directive is callable from an ISR. |
---|
546 | |
---|
547 | This directive will not cause the running task to be |
---|
548 | preempted. Re-initializing RTEMS causes the system date and |
---|
549 | time to be reset to an uninitialized state. Another call to |
---|
550 | @code{@value{DIRPREFIX}clock_set} is required to re-initialize the |
---|
551 | system date and time to application specific specifications. |
---|
552 | |
---|
553 | @c |
---|
554 | @c |
---|
555 | @c |
---|
556 | @page |
---|
557 | @subsection CLOCK_GET_TICKS_PER_SECOND - Get ticks per second |
---|
558 | |
---|
559 | @cindex obtain seconds since epoch |
---|
560 | |
---|
561 | @subheading CALLING SEQUENCE: |
---|
562 | |
---|
563 | @ifset is-C |
---|
564 | @findex rtems_clock_get_ticks_per_second |
---|
565 | @example |
---|
566 | rtems_interval rtems_clock_get_ticks_per_seconds(void); |
---|
567 | @end example |
---|
568 | @end ifset |
---|
569 | |
---|
570 | @ifset is-Ada |
---|
571 | @example |
---|
572 | function Clock_Get_Ticks_Per_Seconds |
---|
573 | return RTEMS.Interval; |
---|
574 | @end example |
---|
575 | @end ifset |
---|
576 | |
---|
577 | @subheading DIRECTIVE STATUS CODES: |
---|
578 | NONE |
---|
579 | |
---|
580 | @subheading DESCRIPTION: |
---|
581 | |
---|
582 | This directive returns the number of clock ticks per second. This |
---|
583 | is strictly based upon the microseconds per clock tick that the |
---|
584 | application has configured. |
---|
585 | |
---|
586 | @subheading NOTES: |
---|
587 | |
---|
588 | This directive is callable from an ISR. |
---|
589 | |
---|
590 | This directive will not cause the running task to be |
---|
591 | preempted. Re-initializing RTEMS causes the system date and |
---|
592 | time to be reset to an uninitialized state. Another call to |
---|
593 | @code{@value{DIRPREFIX}clock_set} is required to re-initialize the |
---|
594 | system date and time to application specific specifications. |
---|
595 | |
---|
596 | @c |
---|
597 | @c |
---|
598 | @c |
---|
599 | @page |
---|
600 | @subsection CLOCK_GET_TICKS_SINCE_BOOT - Get ticks since boot |
---|
601 | |
---|
602 | @cindex obtain ticks since boot |
---|
603 | |
---|
604 | @subheading CALLING SEQUENCE: |
---|
605 | |
---|
606 | @ifset is-C |
---|
607 | @findex rtems_clock_get_ticks_since_boot |
---|
608 | @example |
---|
609 | rtems_interval rtems_clock_get_ticks_since_boot(void); |
---|
610 | @end example |
---|
611 | @end ifset |
---|
612 | |
---|
613 | @ifset is-Ada |
---|
614 | @example |
---|
615 | function Clock_Get_Ticks_Since_Boot |
---|
616 | return RTEMS.Interval; |
---|
617 | @end example |
---|
618 | @end ifset |
---|
619 | |
---|
620 | @subheading DIRECTIVE STATUS CODES: |
---|
621 | NONE |
---|
622 | |
---|
623 | @subheading DESCRIPTION: |
---|
624 | |
---|
625 | This directive returns the number of clock ticks that have elapsed |
---|
626 | since the system was booted. This is the historical measure of uptime |
---|
627 | in an RTEMS system. The newer service |
---|
628 | @code{@value{DIRPREFIX}clock_get_uptime} is another and potentially |
---|
629 | more accurate way of obtaining similar information. |
---|
630 | |
---|
631 | @subheading NOTES: |
---|
632 | |
---|
633 | This directive is callable from an ISR. |
---|
634 | |
---|
635 | This directive will not cause the running task to be |
---|
636 | preempted. Re-initializing RTEMS causes the system date and |
---|
637 | time to be reset to an uninitialized state. Another call to |
---|
638 | @code{@value{DIRPREFIX}clock_set} is required to re-initialize the |
---|
639 | system date and time to application specific specifications. |
---|
640 | |
---|
641 | This directive simply returns the number of times the dirivective |
---|
642 | @code{@value{DIRPREFIX}clock_tick} has been invoked since the |
---|
643 | system was booted. |
---|
644 | |
---|
645 | @c |
---|
646 | @c |
---|
647 | @c |
---|
648 | @page |
---|
649 | @subsection CLOCK_GET_UPTIME - Get the time since boot |
---|
650 | |
---|
651 | @cindex clock get uptime |
---|
652 | @cindex uptime |
---|
653 | |
---|
654 | @subheading CALLING SEQUENCE: |
---|
655 | |
---|
656 | @ifset is-C |
---|
657 | @findex rtems_clock_get_uptime |
---|
658 | @example |
---|
659 | rtems_status_code rtems_clock_get_uptime( |
---|
660 | struct timespec *uptime |
---|
661 | ); |
---|
662 | @end example |
---|
663 | @end ifset |
---|
664 | |
---|
665 | @ifset is-Ada |
---|
666 | @example |
---|
667 | procedure Clock_Get_Uptime ( |
---|
668 | Uptime : out RTEMS.Timespec; |
---|
669 | Result : out RTEMS.Status_Codes |
---|
670 | ); |
---|
671 | @end example |
---|
672 | @end ifset |
---|
673 | |
---|
674 | @subheading DIRECTIVE STATUS CODES: |
---|
675 | @code{@value{RPREFIX}SUCCESSFUL} - clock tick processed successfully@* |
---|
676 | @code{@value{RPREFIX}INVALID_ADDRESS} - @code{time_buffer} is NULL |
---|
677 | |
---|
678 | @subheading DESCRIPTION: |
---|
679 | |
---|
680 | This directive returns the seconds and nanoseconds since the |
---|
681 | system was booted. If the BSP supports nanosecond clock |
---|
682 | accuracy, the time reported will probably be different on every |
---|
683 | call. |
---|
684 | |
---|
685 | @subheading NOTES: |
---|
686 | |
---|
687 | This directive may be called from an ISR. |
---|
688 | |
---|
689 | |
---|
690 | @c |
---|
691 | @c |
---|
692 | @c |
---|
693 | @page |
---|
694 | @subsection CLOCK_SET_NANOSECONDS_EXTENSION - Install the nanoseconds since last tick handler |
---|
695 | |
---|
696 | @cindex clock set nanoseconds extension |
---|
697 | @cindex nanoseconds extension |
---|
698 | @cindex nanoseconds time accuracy |
---|
699 | |
---|
700 | @subheading CALLING SEQUENCE: |
---|
701 | |
---|
702 | @ifset is-C |
---|
703 | @findex rtems_clock_set_nanoseconds_extension |
---|
704 | @example |
---|
705 | rtems_status_code rtems_clock_set_nanoseconds_extension( |
---|
706 | rtems_nanoseconds_extension_routine routine |
---|
707 | ); |
---|
708 | @end example |
---|
709 | @end ifset |
---|
710 | |
---|
711 | @ifset is-Ada |
---|
712 | @example |
---|
713 | NOT SUPPORTED FROM Ada BINDING |
---|
714 | @end example |
---|
715 | @end ifset |
---|
716 | |
---|
717 | @subheading DIRECTIVE STATUS CODES: |
---|
718 | @code{@value{RPREFIX}SUCCESSFUL} - clock tick processed successfully@* |
---|
719 | @code{@value{RPREFIX}INVALID_ADDRESS} - @code{time_buffer} is NULL |
---|
720 | |
---|
721 | @subheading DESCRIPTION: |
---|
722 | |
---|
723 | This directive is used by the Clock device driver to install the |
---|
724 | @code{routine} which will be invoked by the internal RTEMS method used to |
---|
725 | obtain a highly accurate time of day. It is usually called during |
---|
726 | the initialization of the driver. |
---|
727 | |
---|
728 | When the @code{routine} is invoked, it will determine the number of |
---|
729 | nanoseconds which have elapsed since the last invocation of |
---|
730 | the @code{@value{DIRPREFIX}clock_tick} directive. It should do |
---|
731 | this as quickly as possible with as little impact as possible |
---|
732 | on the device used as a clock source. |
---|
733 | |
---|
734 | @subheading NOTES: |
---|
735 | |
---|
736 | This directive may be called from an ISR. |
---|
737 | |
---|
738 | This directive is called as part of every service to obtain the |
---|
739 | current date and time as well as timestamps. |
---|
740 | |
---|
741 | @c |
---|
742 | @c |
---|
743 | @c |
---|
744 | @page |
---|
745 | @subsection CLOCK_TICK - Announce a clock tick |
---|
746 | |
---|
747 | @cindex clock tick |
---|
748 | |
---|
749 | @subheading CALLING SEQUENCE: |
---|
750 | |
---|
751 | @ifset is-C |
---|
752 | @findex rtems_clock_tick |
---|
753 | @example |
---|
754 | rtems_status_code rtems_clock_tick( void ); |
---|
755 | @end example |
---|
756 | @end ifset |
---|
757 | |
---|
758 | @ifset is-Ada |
---|
759 | @example |
---|
760 | procedure Clock_Tick ( |
---|
761 | Result : out RTEMS.Status_Codes |
---|
762 | ); |
---|
763 | @end example |
---|
764 | @end ifset |
---|
765 | |
---|
766 | @subheading DIRECTIVE STATUS CODES: |
---|
767 | @code{@value{RPREFIX}SUCCESSFUL} - clock tick processed successfully |
---|
768 | |
---|
769 | @subheading DESCRIPTION: |
---|
770 | |
---|
771 | This directive announces to RTEMS that a system clock |
---|
772 | tick has occurred. The directive is usually called from the |
---|
773 | timer interrupt ISR of the local processor. This directive |
---|
774 | maintains the system date and time, decrements timers for |
---|
775 | delayed tasks, timeouts, rate monotonic periods, and implements |
---|
776 | timeslicing. |
---|
777 | |
---|
778 | @subheading NOTES: |
---|
779 | |
---|
780 | This directive is typically called from an ISR. |
---|
781 | |
---|
782 | The @code{microseconds_per_tick} and @code{ticks_per_timeslice} |
---|
783 | parameters in the Configuration Table contain the number of |
---|
784 | microseconds per tick and number of ticks per timeslice, |
---|
785 | respectively. |
---|
786 | |
---|