amiga-bootcamp/10_devices/timer.md

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timer.device — Timing and Delays

Overview

timer.device provides precise timing services: delays, time-of-day, and high-resolution timestamps. It has two units:

Unit	Constant	Resolution	Use
0	UNIT_MICROHZ	~2µs (E-clock)	Short, precise delays
1	UNIT_VBLANK	~20ms (VBlank)	Long delays, lower overhead
2	UNIT_ECLOCK	CIA E-clock ticks	Highest resolution timing (OS 2.0+)
3	UNIT_WAITUNTIL	absolute time	Wait until specific time (OS 2.0+)
4	UNIT_WAITECLOCK	E-clock absolute	(OS 2.0+)

---

struct timeval / timerequest

/* devices/timer.h — NDK39 */
struct timeval {
    ULONG tv_secs;    /* seconds */
    ULONG tv_micro;   /* microseconds */
};

struct timerequest {
    struct IORequest tr_node;
    struct timeval   tr_time;
};

---

Simple Delay

struct timerequest *tr = (struct timerequest *)
    CreateIORequest(port, sizeof(struct timerequest));
OpenDevice("timer.device", UNIT_VBLANK, (struct IORequest *)tr, 0);

tr->tr_node.io_Command = TR_ADDREQUEST;
tr->tr_time.tv_secs  = 2;
tr->tr_time.tv_micro = 0;
DoIO((struct IORequest *)tr);   /* blocks for 2 seconds */

CloseDevice((struct IORequest *)tr);
DeleteIORequest((struct IORequest *)tr);

---

Getting Current Time

tr->tr_node.io_Command = TR_GETSYSTIME;
DoIO((struct IORequest *)tr);
Printf("Time: %lu.%06lu\n", tr->tr_time.tv_secs, tr->tr_time.tv_micro);

---

High-Resolution Timing

/* Read E-clock (OS 2.0+): */
struct EClockVal eclock;
ULONG freq = ReadEClock(&eclock);  /* returns ticks/second */
/* eclock.ev_hi, eclock.ev_lo = 64-bit tick count */
/* Typical freq: 709379 Hz (PAL) or 715909 Hz (NTSC) */

---

References

• NDK39: devices/timer.h
• ADCD 2.1: timer.device autodocs