An affordable post-silicon testing framework applied to a RISC-V based microcontroller

The RISC-V architecture is a very attractive option for developing application specific systems needing an affordable yet efficient central processing unit. Post-silicon validation on RISC-V applications has been done in industry for a while, however documentation is scarce. This paper proposes a practical low-cost post-silicon testing framework applied to a RISC-V RV32I based microcontroller. The framework uses FPGA-based emulation as a cornerstone to test the microcontroller before and after its fabrication. The platform only requires a handful of elements like the FPGA, a PC, the fabricated chip and some discrete components, without losing the capacity to functionally validate the design under test and save development testing time by using a re-utilize philosophy.Agencia Nacional de Investigación e Innovació

DFT Research on the Dehydroxylation Reaction of Pyrophyllite 1. First-Principle Molecular Dynamics Simulations

The dehydroxylation of pyrophyllite involves the reaction of OH groups and elimination of water molecules through two possible mechanisms, one involving the bridging hydroxyl groups of an octahedral Al3+ pair and the other two hydroxyl groups reacting across the dioctahedral vacancy. First-principles molecular dynamics simulations at the density functional theory level are used together with the metadynamics algorithm to explore the free-energy surface (FES) of the initial step of the dehydroxylation. We observe that the two possible dehydroxylation mechanisms yield similar activation energies at 0 K, but at high temperatures, the cross mechanism has lower free energy than that of the on-site one. The dehydroxylation process produces different semidehydroxylated intermediates that should be taken into account. The role of the temperature in favoring a dehydroxylation nonconcerted chain mechanism over another is here elucidated, and a novel competitive mechanism, which is assisted by the structural apical oxygens in the high-temperature regime, is proposed.IAC

A compact functional verification flow for a RISC-V 321 based core

The structure of a functional verification flow used for the design of a RISC-V core is presented. The paper offers a guide on the test-planning used and details of the flow architecture, showing how to integrate the Universal Verification Methodology with the required, reference models, while implementing key futures in standard verification environments, such as testing regressions and code and structural coverage. The designed flow is compact yet efficient, making it affordable for small design teams, without requiring extra investment other than the already necessary licenses for RTL synthesis and the eventual fabrication of the chip.Agencia Nacional de Investigación e Innovació

Fault-Tolerant Circuits and Interconnects for Biomedical Implantable Devices

Proyecto de Investigación (Código 1360014) Instituto Tecnológico de Costa Rica. Vicerrectoría de Investigación y Extensión (VIE). Escuela de Ingeniería Electrónica, 2020Los dispositivos médicos implantables (IMDs) son sistemas críticos para la seguridad con requerimientos de potencia muy bajos, los cuales se utilizan para el tratamiento a largo plazo de diferentes condiciones médicas. IMDs utilizan un número de componentes cada vez más elevado (sensores, actuadores, procesadores, bloques de memoria), que tienen que comunicarse entre ellos en un Sistema en Chip (SoC). En este proyecto, diferentes tipos de interconexiones (punto a punto, bus, red en chip) fueron evaluadas considerando su tolerancia a fallas, consumo de potencia y capacidades de comunicación. Como parte de los productos se desarrolló una base de datos escalable sobre sistemas médicos implantables reportados en la literatura hasta el año 2018, con el fin de conocer el estado del arte y las tendencias sobre la incorporación de sistemas electrónicos en este tipo de solución. Basado en este estudio inicial, se procedió a proponer un marco de trabajo de evaluación de interconexiones, el que incorpora un generador de topologías y el flujo de diseño para evaluar estas topologías en términos de potencia y tolerancia a fallas a nivel de simulación, junto con la propuesta de una métrica para comparar diferentes arquitecturas a nivel de pre-síntesis (previo a la consolidación del diseño). Por último, un diseño e implementación a nivel de circuito integrado (IC) de una solución de interconexiones ajustada a IMDs se incorporó en el diseño de un microprocesador a la medida. Este proyecto se desarrolló en el marco de la cooperación con el Centro Médico Erasmus (Erasmus MC) en los Países Bajos y la Universidad Católica del Uruguay

A RISC-V based medical implantable SOC for high voltage a current tissue stimulus

A RISC-V based System on Chip (SoC) for high voltage and current tissue stimulus, targeting implantable medical devices, is presented. The circuit is designed in a 0.18μm HV-CMOS process, including the RISC-V 32RVI based microcontroller core, called Siwa —which includes SPI, UART and GPIO interfaces, a packet-based bus and memory controller, and 8kB SRAM—, combined with several biological tissue stimulus and sensing circuits. The complete test chip (analog+RISC-V) occupies a 5mm2 area but only 0.82mm2 correspond to the RISCV micro-controller, which operates up to 20MHz, with average energy needs of less than 48 pJ/cycle (3pJ STD), and for which several reliability and safety issues were considered.Agencia Nacional de Investigación e Innovació

Siwa: a RISC-V RV32I based micro-controller for implantable medical applications

The design of Siwa1, a compact low power custom system on chip (SoC), targeted for implantable/wearable applications, is reported in this paper. Siwa is based on a RISC-V RV32I architecture. It has a centrally controlled non-pipelined structure, and it includes a control interface for an integrated sensing and stimulation device for biological tissues as well as standard communication interfaces. Siwa was developed from scratch using System Verilog, and implemented in a 180nm CMOS technology; Siwa includes a latch based register file c apable to read and write in one clock cycle with an area 30% smaller and a power consumption 25% lower with respect to an equivalent flip flop implementation; also, it has an estimated average power consumption of 70μW (48pJ/cycle) which is comparable to other micro-controllers commonly used in IMD applications.Agencia Nacional de Investigación e Innovació

Siwa: A custom RISC-V based system on chip (SOC) for low power medical applications

This work introduces the development of Siwa, a RISC-V RV32I 32-bit based core, intended as a flexible control platform for highly integrated implantable biomedical applications, and implemented on a commercial 0.18 m high voltage (HV) CMOS technology. Simulations show that Siwa can outperform commercial micro-controllers commonly used in the medical industry as control units for implantable devices, with energy requirements below the 50 pJ per clock cycle.Agencia Nacional de Investigación e Innovació

DFT Research on the Dehydroxylation Reaction of Pyrophyllite 2. Characterization of Reactants, Intermediates, And Transition States along the Reaction Path

We delineate the dehydroxylation reaction of pyrophyllite in detail by localizing the complete reaction path on the free energy surface obtained previously by Car−Parrinello molecular dynamics and the implemented metadynamics algorithm (Molina-Montes et al. J. Phys. Chem. B2008, 112, 7051). All intermediates were identified, and a transition state search was also undertaken with the PRFO algorithm. The characterization of this reaction and the atomic rearrangement in the intermediates and products at quantum mechanical level were performed for the two reaction paths found previously: (i) direct dehydroxylation through the octahedral hole (cross mechanism) or between contiguous hydroxyl groups (on-site mechanism) and (ii) two-step dehydroxylation assisted by apical oxygens for each of the two steps. New intermediates were found and determined structurally. The structural variations found for all intermediates and transition states are in agreement with experimental results. The formation of these structures indicates that the dehydroxylation process is much more complex than a first-order reaction and can explain the wide range of temperatures for completing the reaction, and these results can be extrapolated to the dehydroxylation of other dioctahedral 2:1 phyllosilicates.IACT (Instituto Andaluz de Ciencias de la Tierra

Exploring the Rehydroxylation Reaction of Pyrophyllite by Ab Initio Molecular Dynamics

We have investigated the process of rehydroxylation of pyrophyllite as a limiting factor to the dehydroxylation upon thermal treatment. Car−Parrinello molecular dynamics simulations based on density functional theory have been used along with the metadynamics algorithm. Two possible rehydroxylation mechanisms reaction have been characterized, related to two possible intermediate structures along the rehydroxylation paths, and both involve the interaction of the apical oxygen atoms. At high temperature, the rehydroxylation reaction is highly competitive (free energy barrier (ΔF) = 1.5 kcal/mol) and inhibits the progress of the dehydroxylation reaction (ΔF = 40 kcal/mol). In addition to the rehydroxylation of the dehydroxylated structure, the water molecule supports the interconversion of the cross and on-site intermediates as well. Thus, rehydroxylation and interconversion among intermediates can justify the wide range of transformations as a function of the temperature observed experimentally.IAC

DFT Research on the Dehydroxylation Reaction of Pyrophyllite 2. Characterization of Reactants, Intermediates, And Transition States along the Reaction Path.

11 pages, 7 figures, 4 tables.We delineate the dehydroxylation reaction of pyrophyllite in detail by localizing the complete reaction path on the free energy surface obtained previously by Car−Parrinello molecular dynamics and the implemented metadynamics algorithm (Molina-Montes et al. J. Phys. Chem. B2008, 112, 7051). All intermediates were identified, and a transition state search was also undertaken with the PRFO algorithm. The characterization of this reaction and the atomic rearrangement in the intermediates and products at quantum mechanical level were performed for the two reaction paths found previously: (i) direct dehydroxylation through the octahedral hole (cross mechanism) or between contiguous hydroxyl groups (on-site mechanism) and (ii) two-step dehydroxylation assisted by apical oxygens for each of the two steps. New intermediates were found and determined structurally. The structural variations found for all intermediates and transition states are in agreement with experimental results. The formation of these structures indicates that the dehydroxylation process is much more complex than a first-order reaction and can explain the wide range of temperatures for completing the reaction, and these results can be extrapolated to the dehydroxylation of other dioctahedral 2:1 phyllosilicates.The authors are thankful to D. Martín- Ramos and A. Martín-Islán for the use of XPowder software and to Centro Técnico de Informática of CSIC, centro de Cálculo del CIEMAT, Centro de Cálculo de Galicia (CESGA), and Centro de Supercomputación de la Universidad de Granada for allowing the use of its computational facilities. E.M.-M. is thankful to MEC (FPU Programme) and CSIC (I3P Programme) for financial support. This work was supported by Spanish MCYT and European.Peer reviewe