Timer HWIP Technical Specification
Overview
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.
Features
- 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
Description
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.
Compatibility
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.