1 | /* Timer_init() |
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2 | * |
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3 | * This routine initializes the timer on the FORCE CPU-386 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 to the Z8036 |
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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) 1989-1997. |
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17 | * On-Line Applications Research Corporation (OAR). |
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18 | * Copyright assigned to U.S. Government, 1994. |
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19 | * |
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20 | * The license and distribution terms for this file may in |
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21 | * the file LICENSE in this distribution or at |
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22 | * http://www.OARcorp.com/rtems/license.html. |
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23 | * |
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24 | * $Id$ |
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25 | */ |
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26 | |
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27 | |
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28 | #include <rtems.h> |
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29 | #include <bsp.h> |
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30 | |
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31 | int Ttimer_val; |
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32 | rtems_boolean Timer_driver_Find_average_overhead; |
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33 | |
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34 | rtems_isr timerisr(); |
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35 | |
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36 | void Timer_initialize() |
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37 | { |
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38 | |
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39 | (void) set_vector( timerisr, 0x38, 0 ); /* install ISR */ |
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40 | |
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41 | Ttimer_val = 0; /* clear timer ISR count */ |
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42 | |
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43 | outport_byte( IERA, 0x40 ); /* disable interrupt */ |
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44 | outport_byte( TBCR, 0x40 ); /* stop the timer */ |
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45 | outport_byte( TBDR, 250 ); /* 250 units */ |
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46 | |
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47 | outport_byte( TBCR, 0x11 ); /* reset it, delay mode, 4X */ |
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48 | #if 0 |
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49 | outport_byte( TBCR, 0x13 ); /* reset it, delay mode, 16X */ |
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50 | #endif |
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51 | |
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52 | outport_byte( IERA, 0x41 ); /* enable interrupt */ |
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53 | |
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54 | } |
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55 | |
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56 | #define AVG_OVERHEAD 3 /* It typically takes 3.0 microseconds */ |
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57 | /* (3 ticks) to start/stop the timer. */ |
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58 | #define LEAST_VALID 4 /* Don't trust a value lower than this */ |
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59 | |
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60 | int Read_timer() |
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61 | { |
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62 | register rtems_unsigned32 clicks; |
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63 | register rtems_unsigned32 total; |
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64 | |
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65 | outport_byte( TBCR, 0x00 ); /* stop the timer */ |
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66 | |
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67 | inport_byte( TBDR, clicks ); |
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68 | |
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69 | total = Ttimer_val + 250 - clicks; |
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70 | |
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71 | outport_byte( TBCR, 0x00 ); /* initial value */ |
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72 | outport_byte( IERA, 0x40 ); /* disable interrupt */ |
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73 | |
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74 | /* ??? Is "do not restore old vector" causing problems? */ |
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75 | |
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76 | if ( Timer_driver_Find_average_overhead == 1 ) |
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77 | return total; /* in one microsecond units */ |
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78 | |
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79 | else { |
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80 | if ( total < LEAST_VALID ) |
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81 | return 0; /* below timer resolution */ |
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82 | return (total - AVG_OVERHEAD); |
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83 | } |
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84 | } |
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85 | |
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86 | rtems_status_code Empty_function( void ) |
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87 | { |
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88 | return RTEMS_SUCCESSFUL; |
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89 | } |
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90 | |
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91 | void Set_find_average_overhead( |
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92 | rtems_boolean find_flag |
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93 | ) |
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94 | { |
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95 | Timer_driver_Find_average_overhead = find_flag; |
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96 | } |
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