Hardware

Introduction

There is the Pinsec toplevel hardware diagram :

RISCV

The RISCV is a 5 stage pipelined CPU with following features :

Instruction cache
Single cycle Barrel shifter
Single cycle MUL, 34 cycle DIV
Interruption support
Dynamic branch prediction
Debug port

AXI4

As previously said, Pinsec integrate an AXI4 bus fabric. AXI4 is not the easiest bus on the Earth but has many advantages like :

A flexible topology
High bandwidth potential
Potential out of order request completion
Easy methods to meets clocks timings
Standard used by many IP
An hand-shaking methodology that fit with SpinalHDL Stream.

From an Area utilization perspective, AXI4 is for sure not the lightest solution, but some techniques could dramatically reduce that issue :

Using Read-Only/Write-Only AXI4 variations where it’s possible
Introducing an Axi4-Shared variation where a new ARW channel is introduced to replace AR and AW channels. This solution divide resources usage by two for the address decoding and the address arbitration.
Depending the interconnect implementation, if masters doesn’t use the R/B channels ready, this path will be removed until each slaves at synthesis, which relax timings.
As the AXI4 spec suggest, the interconnect can expand the transactions ID by aggregating the corresponding input port id. This allow the interconnect to have an infinite number of pending request and also to support out of order completion with a negligible area cost (transaction id expand).

The Pinsec interconnect doesn’t introduce latency cycles.

APB3

In Pinsec, all peripherals implement an APB3 bus to be interfaced. The APB3 choice was motivated by following reasons :

Very simple bus (no burst)
Use very few resources
Standard used by many IP

Generate the RTL

To generate the RTL, you have multiple solutions :

You can download the SpinalHDL source code, and then run :

sbt "project SpinalHDL-lib" "run-main spinal.lib.soc.pinsec.Pinsec"

Or you can create your own main into your own SBT project and then run it :

import spinal.lib.soc.pinsec._

object PinsecMain{
  def main(args: Array[String]) {
    SpinalVhdl(new Pinsec(100 MHz))
    SpinalVerilog(new Pinsec(100 MHz))
  }
}

Note

Currently, only the verilog version was tested in simulation and in FPGA because the last release of GHDL is not compatible with cocotb.