1 | /* Timer_init() |
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2 | * |
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3 | * This routine initializes the Tick Timer 1 on the MVME162 board. |
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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: This routine will not work if the optimizer is enabled |
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10 | * for some compilers. The multiple writes |
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11 | * may be optimized away. |
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12 | * |
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13 | * It is important that the timer start/stop overhead be |
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14 | * determined when porting or modifying this code. |
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15 | * |
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16 | * COPYRIGHT (c) 1989-1999. |
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17 | * On-Line Applications Research Corporation (OAR). |
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18 | * |
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19 | * The license and distribution terms for this file may be |
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20 | * found in the file LICENSE in this distribution or at |
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21 | * http://www.OARcorp.com/rtems/license.html. |
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22 | * |
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23 | * Modifications of respective RTEMS file: COPYRIGHT (c) 1994. |
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24 | * EISCAT Scientific Association. M.Savitski |
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25 | * |
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26 | * This material is a part of the MVME162 Board Support Package |
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27 | * for the RTEMS executive. Its licensing policies are those of the |
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28 | * RTEMS above. |
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29 | * |
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30 | * $Id$ |
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31 | */ |
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32 | |
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33 | #include <rtems.h> |
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34 | #include <bsp.h> |
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35 | |
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36 | /* Periodic tick interval */ |
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37 | #define TICK_INTERVAL 0x10000U |
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38 | #define TIMER_INT_LEVEL 6 |
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39 | |
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40 | rtems_unsigned32 Ttimer_val; |
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41 | rtems_boolean Timer_driver_Find_average_overhead; |
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42 | |
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43 | rtems_isr timerisr(); |
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44 | |
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45 | void Timer_initialize() |
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46 | { |
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47 | (void) set_vector( timerisr, VBR0 * 0x10 + 0x8, 0 ); |
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48 | |
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49 | Ttimer_val = 0; /* clear timer ISR count */ |
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50 | lcsr->vector_base |= MASK_INT; /* unmask VMEchip2 interrupts */ |
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51 | lcsr->intr_clear |= 0x01000000; /* clear pending interrupt */ |
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52 | lcsr->to_ctl = 0xE7; /* prescaler to 1 MHz (see Appendix A1) */ |
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53 | lcsr->timer_cmp_1 = TICK_INTERVAL; |
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54 | lcsr->timer_cnt_1 = 0; /* clear counter */ |
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55 | lcsr->board_ctl |= 7; /* increment, reset-on-compare, */ |
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56 | /* and clear-overflow-cnt */ |
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57 | |
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58 | lcsr->intr_level[0] |= TIMER_INT_LEVEL; /* set int level */ |
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59 | lcsr->intr_ena |= 0x01000000; /* enable tick timer 1 interrupt */ |
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60 | } |
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61 | |
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62 | #define AVG_OVERHEAD 3U /* It typically takes 3.0 microseconds */ |
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63 | /* (3 countdowns) to start/stop the timer. */ |
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64 | #define LEAST_VALID 10U /* Don't trust a value lower than this */ |
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65 | |
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66 | int Read_timer() |
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67 | { |
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68 | rtems_unsigned32 total; |
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69 | |
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70 | total = (Ttimer_val * TICK_INTERVAL) + lcsr->timer_cnt_1; |
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71 | |
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72 | if ( Timer_driver_Find_average_overhead == 1 ) |
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73 | return total; /* in one-half microsecond units */ |
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74 | |
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75 | if ( total < LEAST_VALID ) |
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76 | return 0; /* below timer resolution */ |
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77 | |
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78 | return (total-AVG_OVERHEAD) >> 1; |
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79 | } |
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80 | |
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81 | |
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82 | rtems_status_code Empty_function( void ) |
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83 | { |
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84 | return RTEMS_SUCCESSFUL; |
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85 | } |
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86 | |
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87 | void Set_find_average_overhead( |
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88 | rtems_boolean find_flag |
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89 | ) |
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90 | { |
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91 | Timer_driver_Find_average_overhead = find_flag; |
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92 | } |
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