| /* | |
| * This file is part of the DOSMid project. | |
| * Copyright (C) Mateusz Viste 2014-2015 | |
| * | |
| * This file contains the implementation of a more precise timer than that | |
| * provided by DOS. Routines are provided to increase the PIT clock rate to | |
| * around 1165 interrupts per second, for a granularity of close to 858 | |
| * microseconds between clock pulses, rather than the 55 milliseconds between | |
| * standard PC clock pulses (18.2 times/second). | |
| * | |
| * Note that the timer_start() routine must be called before the timer_read() | |
| * routines will work, and that the timer_stop() routine MUST be called | |
| * before the program terminates, or the machine will be toasted. For this | |
| * reason, timer_init() installs the timer_stop() routine to be called at | |
| * program exit. | |
| */ | |
| #ifndef timer_h_sentinel | |
| #define timer_h_sentinel | |
| /* reset the timer value, this can be used by the application to make sure | |
| * no timer wrap occurs during critical parts of the code flow */ | |
| void timer_reset(void); | |
| /* This routine will stop the fast clock if it is going. It has void return | |
| * value so that it can be an exit procedure. */ | |
| void timer_stop(void); | |
| /* This routine will start the fast clock rate by installing the | |
| * handle_clock routine as the interrupt service routine for the clock | |
| * interrupt and then setting the interrupt rate up to its higher speed | |
| * by programming the 8253 timer chip. | |
| * This routine does nothing if the clock rate is already set to | |
| * its higher rate, but then it returns -1 to indicate the error. */ | |
| void timer_init(void); | |
| /* This routine will return the present value of the time, which is | |
| * read from the nowtime structure. Interrupts are disabled during this | |
| * time to prevent the clock from changing while it is being read. */ | |
| void timer_read(unsigned long *res); | |
| #endif |