Timer Unit

SH4 CPU peripheral providing timers and counters More...

Topics
	Channels
	TMU channel constants
	Direct-Access
	Low-level timer driver
	Primary Timer
	Primary timer used by the kernel.
	Sleeping
	Low-level thread sleeping
	Uptime
	Maintaining time since system boot.

Files
file	timer.h
	Low-level timer functionality.

Detailed Description

SH4 CPU peripheral providing timers and counters

The Dreamcast's SH4 includes an on-chip Timer Unit (TMU) containing 3 independent 32-bit channels (TMU0-TMU2). Each channel provides a down-counter with automatic reload and can be configured to use 1 of 7 divider circuits for its input clock. By default, KOS uses the fastest input clock for each TMU channel, providing a maximum internal resolution of 80ns ticks.

Warning

Under normal circumstances, all 3 TMU channels are reserved by KOS for various OS-related purposes. If you need a free general-purpose interval timer, consider using the Watchdog Timer.

Note

90% of the time, you will never have a need to directly interact with this API, as it's mostly used as a kernel-level driver which backs other APIs. For example, querying for ticks, fetching the current timestamp, or putting a thread to sleep is typically done via the standard C, C++, or POSIX APIs.