Timer HWIP Technical Specification



This document specifies RISC-V Timer hardware IP functionality. This module conforms to the Comportable guideline for peripheral functionality. See that document for integration overview within the broader top level system.


  • 64-bit timer with 12-bit prescaler and 8-bit step register
  • Compliant with RISC-V privileged specification v1.11
  • Configurable number of timers per hart and number of harts


The timer module provides a configurable number of 64-bit counters where each counter increments by a step value whenever the prescaler times out. Each timer generates an interrupt if the counter reaches (or is above) a programmed value. The timer is intended to be used by the processors to check the current time relative to the reset or the system power-on.

In this version, the timer doesn’t consider low-power modes and assumes the clock is neither turned off nor changed during runtime.


The timer IP provides memory-mapped registers equivalent to mtime and mtimecmp which can be used as the machine-mode timer registers defined in the RISC-V privileged spec. Additional features such as prescaler, step, and a configurable number of timers and harts have been added.