[ac7d5ef0] | 1 | /* Timer_init() |
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| 2 | * |
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| 3 | * This routine initializes the MC68230 timer on the Motorola IDP 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 MC68230 |
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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 | * Code Modified for the MC68230 by Doug McBride, Colorado Space Grant College |
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| 17 | * |
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[08311cc3] | 18 | * COPYRIGHT (c) 1989-1999. |
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[ac7d5ef0] | 19 | * On-Line Applications Research Corporation (OAR). |
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| 20 | * |
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[98e4ebf5] | 21 | * The license and distribution terms for this file may be |
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| 22 | * found in the file LICENSE in this distribution or at |
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[c3db3251] | 23 | * http://www.rtems.com/license/LICENSE. |
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[ac7d5ef0] | 24 | * |
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| 25 | * $Id$ |
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| 26 | */ |
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| 27 | |
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| 28 | |
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[88d594a] | 29 | #include <rtems.h> |
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| 30 | #include <bsp.h> |
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[19fd334] | 31 | #include <motorola/mc68230.h> |
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[ac7d5ef0] | 32 | |
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| 33 | #define TIMER_VECTOR 0x4D |
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| 34 | |
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| 35 | int Ttimer_val; |
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| 36 | rtems_boolean Timer_driver_Find_average_overhead; |
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| 37 | |
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| 38 | rtems_isr timerisr(); |
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| 39 | |
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| 40 | void Timer_initialize() |
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| 41 | { |
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| 42 | (void) set_vector( timerisr, TIMER_VECTOR, 0 ); /* install ISR */ |
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| 43 | |
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| 44 | Ttimer_val = 0; /* clear timer ISR count */ |
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| 45 | |
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| 46 | /* some PI/T initialization stuff here */ |
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| 47 | /* Set up the interrupt vector on the MC68230 chip: |
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| 48 | TIVR = TIMER_VECTOR; */ |
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| 49 | MC68230_WRITE (TIVR, TIMER_VECTOR); |
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| 50 | |
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| 51 | /* Set CPRH through CPRL to maximum count to reduce interrupt overhead |
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| 52 | CPRH = 0xFF; |
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| 53 | CPRM = 0xFF; |
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| 54 | CPRL = 0xFF; */ |
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| 55 | MC68230_WRITE (CPRH, 0xFF); |
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| 56 | MC68230_WRITE (CPRM, 0xFF); |
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| 57 | MC68230_WRITE (CPRL, 0xFF); |
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| 58 | |
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| 59 | /* Enable timer and use it as an external periodic interrupt generator |
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| 60 | TCR = 0xA1; */ |
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| 61 | MC68230_WRITE (TCR, 0xA1); |
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| 62 | |
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| 63 | } |
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| 64 | |
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| 65 | #define AVG_OVERHEAD 9 /* may not be right -- do this later */ |
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| 66 | #define LEAST_VALID 10 /* Don't trust a value lower than this */ |
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| 67 | |
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| 68 | int Read_timer() |
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| 69 | { |
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| 70 | rtems_unsigned8 data; |
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| 71 | rtems_unsigned8 msb, osb, lsb; |
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| 72 | rtems_unsigned32 remaining, total; |
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| 73 | |
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| 74 | /* Disable timer so that timer can be read |
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| 75 | data = TCR; |
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| 76 | TCR = (data & 0xFE); */ |
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| 77 | MC68230_READ (TCR, data); |
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| 78 | MC68230_WRITE (TCR, (data & 0xFE)); |
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| 79 | |
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| 80 | /* Read the counter value |
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| 81 | msb = CNTRH; |
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| 82 | osb = CNTRM; |
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| 83 | lsb = CNTRL; */ |
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| 84 | MC68230_READ (CNTRH, msb); |
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| 85 | MC68230_READ (CNTRM, osb); |
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| 86 | MC68230_READ (CNTRL, lsb); |
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| 87 | |
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| 88 | /* Calculate the time so far */ |
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| 89 | remaining = 0x1000000 - ((msb << 16) + (osb << 8) + lsb); |
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| 90 | total = (Ttimer_val * 0x1000000) + remaining; |
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| 91 | |
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| 92 | /* Enable timer so that timer can continue |
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| 93 | TCR = 0xA1; */ |
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| 94 | MC68230_WRITE (TCR, 0xA1); |
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| 95 | |
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| 96 | /* do not restore old vector */ |
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| 97 | if ( Timer_driver_Find_average_overhead == 1 ) |
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| 98 | return total; /* in countdown units */ |
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| 99 | |
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| 100 | if ( total < LEAST_VALID ) |
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| 101 | return 0; /* below timer resolution */ |
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| 102 | |
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| 103 | /* Clocked at 6.5 Mhz */ |
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| 104 | /* Avoid floating point problems, be lazy, and return the total minus |
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| 105 | the average overhead */ |
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| 106 | return (total - AVG_OVERHEAD); |
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| 107 | } |
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| 108 | |
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| 109 | rtems_status_code Empty_function( void ) |
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| 110 | { |
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| 111 | return RTEMS_SUCCESSFUL; |
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| 112 | } |
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| 113 | |
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| 114 | void Set_find_average_overhead( |
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| 115 | rtems_boolean find_flag |
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| 116 | ) |
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| 117 | { |
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| 118 | Timer_driver_Find_average_overhead = find_flag; |
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| 119 | } |
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