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[/] [openrisc/] [trunk/] [rtos/] [rtems/] [c/] [src/] [lib/] [libbsp/] [m68k/] [idp/] [timer/] [timer.c] - Rev 593
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/* Timer_init() * * This routine initializes the MC68230 timer on the Motorola IDP board. * * Input parameters: NONE * * Output parameters: NONE * * NOTE: This routine will not work if the optimizer is enabled * for some compilers. The multiple writes to the MC68230 * may be optimized away. * * It is important that the timer start/stop overhead be * determined when porting or modifying this code. * * Code Modified for the MC68230 by Doug McBride, Colorado Space Grant College * * COPYRIGHT (c) 1989-1999. * On-Line Applications Research Corporation (OAR). * * The license and distribution terms for this file may be * found in the file LICENSE in this distribution or at * http://www.OARcorp.com/rtems/license.html. * * $Id: timer.c,v 1.2 2001-09-27 12:00:12 chris Exp $ */ #include <rtems.h> #include <bsp.h> #include <motorola/mc68230.h> #define TIMER_VECTOR 0x4D int Ttimer_val; rtems_boolean Timer_driver_Find_average_overhead; rtems_isr timerisr(); void Timer_initialize() { (void) set_vector( timerisr, TIMER_VECTOR, 0 ); /* install ISR */ Ttimer_val = 0; /* clear timer ISR count */ /* some PI/T initialization stuff here */ /* Set up the interrupt vector on the MC68230 chip: TIVR = TIMER_VECTOR; */ MC68230_WRITE (TIVR, TIMER_VECTOR); /* Set CPRH through CPRL to maximum count to reduce interrupt overhead CPRH = 0xFF; CPRM = 0xFF; CPRL = 0xFF; */ MC68230_WRITE (CPRH, 0xFF); MC68230_WRITE (CPRM, 0xFF); MC68230_WRITE (CPRL, 0xFF); /* Enable timer and use it as an external periodic interrupt generator TCR = 0xA1; */ MC68230_WRITE (TCR, 0xA1); } #define AVG_OVERHEAD 9 /* may not be right -- do this later */ #define LEAST_VALID 10 /* Don't trust a value lower than this */ int Read_timer() { rtems_unsigned8 data; rtems_unsigned8 msb, osb, lsb; rtems_unsigned32 remaining, total; /* Disable timer so that timer can be read data = TCR; TCR = (data & 0xFE); */ MC68230_READ (TCR, data); MC68230_WRITE (TCR, (data & 0xFE)); /* Read the counter value msb = CNTRH; osb = CNTRM; lsb = CNTRL; */ MC68230_READ (CNTRH, msb); MC68230_READ (CNTRM, osb); MC68230_READ (CNTRL, lsb); /* Calculate the time so far */ remaining = 0x1000000 - ((msb << 16) + (osb << 8) + lsb); total = (Ttimer_val * 0x1000000) + remaining; /* Enable timer so that timer can continue TCR = 0xA1; */ MC68230_WRITE (TCR, 0xA1); /* do not restore old vector */ if ( Timer_driver_Find_average_overhead == 1 ) return total; /* in countdown units */ if ( total < LEAST_VALID ) return 0; /* below timer resolution */ /* Clocked at 6.5 Mhz */ /* Avoid floating point problems, be lazy, and return the total minus the average overhead */ return (total - AVG_OVERHEAD); } rtems_status_code Empty_function( void ) { return RTEMS_SUCCESSFUL; } void Set_find_average_overhead( rtems_boolean find_flag ) { Timer_driver_Find_average_overhead = find_flag; }
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