README.md

MyCLINT

RISC-V Core Local Interrupt Controller (CLINT) written in Verilog. The initial focus is for it to work as a IOb-SoC-VexRiscv peripheral.

This repository was archived since we are now working in https://github.com/IObundle/iob-clint. Please go there for further development.

Simulation

To simulate the CLINT unit the user can use both "icarus verilog" and "verilator". Simply run:

make sim-run
# or
make sim-run SIMULATOR=verilator

Before running new simulation do not forget to run make sim-clean.

Register Map

This clint unit follows the RISC-V Specification.

Register	Base Address	Width	Privilege Level	Functionality
MSIP	xxxx0000	n*4 Bytes	Machine	Inter-processor (or software) interrupts
MTIMECMP	xxxx4000	n*8 Bytes	Machine	Timer events
MTIME	xxxxbff8	8 Bytes	Machine	Fixed-frequency counter

*note: n correspond to the number of HART's (hardware threads) on a system. The system has been tested to work with 1 HART.

Machine-level Timer Device (MTIMER)

The MTIMER hardware component corresponds to the MTIME and MTIMECMP registers. On reset the MTIME register is set to have all bits at 0 and the MTIMECMP register has all bits at 1. If the value in MTIME is greater than the value stored in MTIMECMP than the Machine Timer Interrupt is enabled and the clint mtip output is set to high.

Machine-level Software Interrupt Device (MSWI)

The MSWI hardware component corresponds to the MSIP register. On reset the MSIP register is set to 0. The each Machine Software Interrupt is wired to the corresponding MSIP register. In accordance the clint msip output is set to high if the less significant bit of the corresponding MSIP registers is set to 1. In the MSIP register all bits except the less significant one should be hardwired to 0.

Supervisor-level Software Interrupt Device (SSWI)

(TO DO)

References

• RISC-V Advanced Core Local Interruptor Specification -> https://github.com/riscv/riscv-aclint/blob/main/riscv-aclint.adoc
• IOb-SoC -> https://github.com/IObundle/iob-soc
• CVA6 CLINT -> https://github.com/openhwgroup/cva6/tree/master/corev_apu/clint
• Bare Metal Interrupt Software -> https://github.com/five-embeddev/riscv-scratchpad/tree/master/baremetal-startup-c/src