Under-the-cell routing to improve manufacturability

The progressive miniaturization of technology and the unequal scalability of the BEOL and FEOL layers aggravate the routing congestion problem and have a negative impact on manufacturability. Standard cells are designed in a way that they can be treated as black boxes during physical design. However, this abstraction often prevents an efficient use of its internal free resources. This paper proposes an effective approach for using internal routing resources without sacrificing modularity. By using cell generation tools for regular layouts, libraries are enriched with cell instances that have lateral pins and allow under-the-cell connections between adjacent cells, thus reducing pin count, via count and routing congestion. An approach to generate cells with regular layouts and lateral pins is proposed. Additionally, algorithms to maximize the impact of under-the-cell routing are presented. The proposed techniques are integrated in an industrial design flow. Experimental results show a significant reduction of design rule check violations with negligible impact on timing.Peer ReviewedPostprint (author's final draft

Bifurcation-based parameter tuning in a model of the GnRH pulse and surge generator

We investigate a model of the GnRH pulse and surge generator, with the definite aim of constraining the model GnRH output with respect to a physiologically relevant list of specifications. The alternating pulse and surge pattern of secretion results from the interaction between a GnRH secreting system and a regulating system exhibiting fast-slow dynamics. The mechanisms underlying the behavior of the model are reminded from the study of the Boundary-Layer System according to the "dissection method" principle. Using singular perturbation theory, we describe the sequence of bifurcations undergone by the regulating (FitzHugh-Nagumo) system, encompassing the rarely investigated case of homoclinic connexion. Basing on pure dynamical considerations, we restrict the space of parameter search for the regulating system and describe a foliation of this restricted space, whose leaves define constant duration ratios between the surge and the pulsatility phase in the whole system. We propose an algorithm to fix the parameter values to also meet the other prescribed ratios dealing with amplitude and frequency features of the secretion signal. We finally apply these results to illustrate the dynamics of GnRH secretion in the ovine species and the rhesus monkey

Algorithmic techniques for physical design : macro placement and under-the-cell routing

With the increase of chip component density and new manufacturability constraints imposed by modern technology nodes, the role of algorithms for electronic design automation is key to the successful implementation of integrated circuits. Two of the critical steps in the physical design flows are macro placement and ensuring all design rules are honored after timing closure. This thesis proposes contributions to help in these stages, easing time-consuming manual steps and helping physical design engineers to obtain better layouts in reduced turnaround time. The first contribution is under-the-cell routing, a proposal to systematically connect standard cell components via lateral pins in the lower metal layers. The aim is to reduce congestion in the upper metal layers caused by extra metal and vias, decreasing the number of design rule violations. To allow cells to connect by abutment, a standard cell library is enriched with instances containing lateral pins in a pre-selected sharing track. Algorithms are proposed to maximize the numbers of connections via lateral connection by mapping placed cell instances to layouts with lateral pins, and proposing local placement modifications to increase the opportunities for such connections. Experimental results show a significant decrease in the number of pins, vias, and in number of design rule violations, with negligible impact on wirelength and timing. The second contribution, done in collaboration with eSilicon (a leading ASIC design company), is the creation of HiDaP, a macro placement tool for modern industrial designs. The proposed approach follows a multilevel scheme to floorplan hierarchical blocks, composed of macros and standard cells. By exploiting RTL information available in the netlist, the dataflow affinity between these blocks is modeled and minimized to find a macro placement with good wirelength and timing properties. The approach is further extended to allow additional engineer input, such as preferred macro locations, and also spectral and force methods to guide the floorplanning search. Experimental results show that the layouts generated by HiDaP outperforms those obtained by a state-of-the-art EDA physical design software, with similar wirelength and better timing when compared to manually designed tape-out ready macro placements. Layouts obtained by HiDaP have successfully been brought to near timing closure with one to two rounds of small modifications by physical design engineers. HiDaP has been fully integrated in the design flows of the company and its development remains an ongoing effort.A causa de l'increment de la densitat de components en els xip i les noves restriccions de disseny imposades pels últims nodes de fabricació, el rol de l'algorísmia en l'automatització del disseny electrònic ha esdevingut clau per poder implementar circuits integrats. Dos dels passos crucials en el procés de disseny físic és el placement de macros i assegurar la correcció de les regles de disseny un cop les restriccions de timing del circuit són satisfetes. Aquesta tesi proposa contribucions per ajudar en aquests dos reptes, facilitant laboriosos passos manuals en el procés i ajudant als enginyers de disseny físic a obtenir millors resultats en menys temps. La primera contribució és el routing "under-the-cell", una proposta per connectar cel·les estàndard usant pins laterals en les capes de metall inferior de manera sistemàtica. L'objectiu és reduir la congestió en les capes de metall superior causades per l'ús de metall i vies, i així disminuir el nombre de violacions de regles de disseny. Per permetre la connexió lateral de cel·les, estenem una llibreria de cel·les estàndard amb dissenys que incorporen connexions laterals. També proposem modificacions locals al placement per permetre explotar aquest tipus de connexions més sovint. Els resultats experimentals mostren una reducció significativa en el nombre de pins, vies i nombre de violacions de regles de disseny, amb un impacte negligible en wirelength i timing. La segona contribució, desenvolupada en col·laboració amb eSilicon (una empresa capdavantera en disseny ASIC), és el desenvolupament de HiDaP, una eina de macro placement per a dissenys industrials actuals. La proposta segueix un procés multinivell per fer el floorplan de blocks jeràrquics, formats per macros i cel·les estàndard. Mitjançant la informació RTL disponible en la netlist, l'afinitat de dataflow entre els mòduls es modela i minimitza per trobar macro placements amb bones propietats de wirelength i timing. La proposta també incorpora la possibilitat de rebre input addicional de l'enginyer, com ara suggeriments de les posicions de les macros. Finalment, també usa mètodes espectrals i de forçes per guiar la cerca de floorplans. Els resultats experimentals mostren que els dissenys generats amb HiDaP són millors que els obtinguts per eines comercials capdavanteres de EDA. Els resultats també mostren que els dissenys presentats poden obtenir un wirelength similar i millor timing que macro placements obtinguts manualment, usats per fabricació. Alguns dissenys obtinguts per HiDaP s'han dut fins a timing-closure en una o dues rondes de modificacions incrementals per part d'enginyers de disseny físic. L'eina s'ha integrat en el procés de disseny de eSilicon i el seu desenvolupament continua més enllà de les aportacions a aquesta tesi.Postprint (published version

Algorithmic techniques for physical design : macro placement and under-the-cell routing

With the increase of chip component density and new manufacturability constraints imposed by modern technology nodes, the role of algorithms for electronic design automation is key to the successful implementation of integrated circuits. Two of the critical steps in the physical design flows are macro placement and ensuring all design rules are honored after timing closure. This thesis proposes contributions to help in these stages, easing time-consuming manual steps and helping physical design engineers to obtain better layouts in reduced turnaround time. The first contribution is under-the-cell routing, a proposal to systematically connect standard cell components via lateral pins in the lower metal layers. The aim is to reduce congestion in the upper metal layers caused by extra metal and vias, decreasing the number of design rule violations. To allow cells to connect by abutment, a standard cell library is enriched with instances containing lateral pins in a pre-selected sharing track. Algorithms are proposed to maximize the numbers of connections via lateral connection by mapping placed cell instances to layouts with lateral pins, and proposing local placement modifications to increase the opportunities for such connections. Experimental results show a significant decrease in the number of pins, vias, and in number of design rule violations, with negligible impact on wirelength and timing. The second contribution, done in collaboration with eSilicon (a leading ASIC design company), is the creation of HiDaP, a macro placement tool for modern industrial designs. The proposed approach follows a multilevel scheme to floorplan hierarchical blocks, composed of macros and standard cells. By exploiting RTL information available in the netlist, the dataflow affinity between these blocks is modeled and minimized to find a macro placement with good wirelength and timing properties. The approach is further extended to allow additional engineer input, such as preferred macro locations, and also spectral and force methods to guide the floorplanning search. Experimental results show that the layouts generated by HiDaP outperforms those obtained by a state-of-the-art EDA physical design software, with similar wirelength and better timing when compared to manually designed tape-out ready macro placements. Layouts obtained by HiDaP have successfully been brought to near timing closure with one to two rounds of small modifications by physical design engineers. HiDaP has been fully integrated in the design flows of the company and its development remains an ongoing effort.A causa de l'increment de la densitat de components en els xip i les noves restriccions de disseny imposades pels últims nodes de fabricació, el rol de l'algorísmia en l'automatització del disseny electrònic ha esdevingut clau per poder implementar circuits integrats. Dos dels passos crucials en el procés de disseny físic és el placement de macros i assegurar la correcció de les regles de disseny un cop les restriccions de timing del circuit són satisfetes. Aquesta tesi proposa contribucions per ajudar en aquests dos reptes, facilitant laboriosos passos manuals en el procés i ajudant als enginyers de disseny físic a obtenir millors resultats en menys temps. La primera contribució és el routing "under-the-cell", una proposta per connectar cel·les estàndard usant pins laterals en les capes de metall inferior de manera sistemàtica. L'objectiu és reduir la congestió en les capes de metall superior causades per l'ús de metall i vies, i així disminuir el nombre de violacions de regles de disseny. Per permetre la connexió lateral de cel·les, estenem una llibreria de cel·les estàndard amb dissenys que incorporen connexions laterals. També proposem modificacions locals al placement per permetre explotar aquest tipus de connexions més sovint. Els resultats experimentals mostren una reducció significativa en el nombre de pins, vies i nombre de violacions de regles de disseny, amb un impacte negligible en wirelength i timing. La segona contribució, desenvolupada en col·laboració amb eSilicon (una empresa capdavantera en disseny ASIC), és el desenvolupament de HiDaP, una eina de macro placement per a dissenys industrials actuals. La proposta segueix un procés multinivell per fer el floorplan de blocks jeràrquics, formats per macros i cel·les estàndard. Mitjançant la informació RTL disponible en la netlist, l'afinitat de dataflow entre els mòduls es modela i minimitza per trobar macro placements amb bones propietats de wirelength i timing. La proposta també incorpora la possibilitat de rebre input addicional de l'enginyer, com ara suggeriments de les posicions de les macros. Finalment, també usa mètodes espectrals i de forçes per guiar la cerca de floorplans. Els resultats experimentals mostren que els dissenys generats amb HiDaP són millors que els obtinguts per eines comercials capdavanteres de EDA. Els resultats també mostren que els dissenys presentats poden obtenir un wirelength similar i millor timing que macro placements obtinguts manualment, usats per fabricació. Alguns dissenys obtinguts per HiDaP s'han dut fins a timing-closure en una o dues rondes de modificacions incrementals per part d'enginyers de disseny físic. L'eina s'ha integrat en el procés de disseny de eSilicon i el seu desenvolupament continua més enllà de les aportacions a aquesta tesi

Wild oscillations in a nonlinear neuron model with resets: (II) Mixed-mode oscillations

This work continues the analysis of complex dynamics in a class of bidimensional nonlinear hybrid dynamical systems with resets modeling neuronal voltage dynamics with adaptation and spike emission. We show that these models can generically display a form of mixed-mode oscillations (MMOs), which are trajectories featuring an alternation of small oscillations with spikes or bursts (multiple consecutive spikes). The mechanism by which these are generated relies fundamentally on the hybrid structure of the flow: invariant manifolds of the continuous dynamics govern small oscillations, while discrete resets govern the emission of spikes or bursts, contrasting with classical MMO mechanisms in ordinary differential equations involving more than three dimensions and generally relying on a timescale separation. The decomposition of mechanisms reveals the geometrical origin of MMOs, allowing a relatively simple classification of points on the reset manifold associated to specific numbers of small oscillations. We show that the MMO pattern can be described through the study of orbits of a discrete adaptation map, which is singular as it features discrete discontinuities with unbounded left- and right-derivatives. We study orbits of the map via rotation theory for discontinuous circle maps and elucidate in detail complex behaviors arising in the case where MMOs display at most one small oscillation between each consecutive pair of spikes

A multisensory approach to spatial updating: the case of mental rotations

Mental rotation is the capacity to predict the outcome of spatial relationships after a change in viewpoint. These changes arise either from the rotation of the test object array or from the rotation of the observer. Previous studies showed that the cognitive cost of mental rotations is reduced when viewpoint changes result from the observer’s motion, which was explained by the spatial updating mechanism involved during self-motion. However, little is known about how various sensory cues available might contribute to the updating performance. We used a Virtual Reality setup in a series of experiments to investigate table-top mental rotations under different combinations of modalities among vision, body and audition. We found that mental rotation performance gradually improved when adding sensory cues to the moving observer (from None to Body or Vision and then to Body & Audition or Body & Vision), but that the processing time drops to the same level for any of the sensory contexts. These results are discussed in terms of an additive contribution when sensory modalities are co-activated to the spatial updating mechanism involved during self-motion. Interestingly, this multisensory approach can account for different findings reported in the literature

Occurrence of microcystins along the Guadiana estuary

Blooms of toxic cyanobacteria develop regularly during summer and early autumn in the Guadiana River (South of Iberian Peninsula). Microcystis aeruginosa, Aphanizomenon flos-aquae, Oscillatoria spp. and Anabaena spp. have been identified in previous studies as the main toxic cyanobacteria present. With the closure of the Alqueva dam and its new policy of water retention, the present project focused on the effect of these new hydrological conditions to toxic cyanobacteria bloom formations in the Guadiana estuary. This article shows data collected from three sampling stations located along the estuary during the spring of 2002. Physical and chemical parameters (temperature, salinity, turbidity and nutrients (dissolved nitrate, silicate and phosphate)) and biological characteristics of the water (chlorophyll a and phytoplankton composition) were evaluated, as well as microcystin (MC) content in particulate material using HPLC-PDA. Microcystis sp. was the dominant toxic cyanobacteria in the collected water samples. Results suggest the existence of a longitudinal gradient in toxin content directly related to the development of temperature, salinity and nutritional ratio gradients along the estuary, and indirectly related to the turbidity of the water. At least five MC variants were observed and quantified as MC-LR equivalents (MC-LR Equiv.). The total MC concentrations in particulate material varied from 0.0 to above 1.0 μg MCLR Equiv.·L-1, with higher values always observed at the freshwater station. Finally, higher dissolved silica concentrations were found in the water column when compared to results from previous years. These differences reflect changes in the Guadiana ecohydrological status which are probably related to the Alqueva dam construction.La formación de blooms de cianobacterias tóxicas se produce regularmente durante los meses de verano y principios del otoño en el Río Guadiana (Sur de la Península Ibérica). Entre las diferentes cianobacterias potencialmente tóxicas estudios previos han identificado a especies como Microcystis aeruginosa, Aphanizomenon flos-aquae, Oscillatoria spp. y Anabaena spp. Con la puesta en funcionamiento de la presa de Alqueva y su nueva política de retención de aguas, se elaboró el presente proyecto enfocado hacia el estudio del efecto de las nuevas condiciones hidrológicas sobre la formación de blooms de cianobacterias tóxicas en el estuario del Guadiana. Este artículo muestra los datos obtenidos en tres estaciones de muestreo localizadas a lo largo del estuario del Guadiana durante la primavera del año 2002. Se analizaron parámetros físico-químicos (temperatura, salinidad, turbidez y nutrientes (nitrato, silicato y fosfato disueltos)) y características biológicas del agua (clorofila a y composición fitoplanctónica), así como el contenido de microcistina (MC) en el material particulado cuantificado por HPLC-PDA, en tres estaciones de muestreo situadas a lo largo del estuario. Microcystis sp. fue la cianobacteria tóxica predominante en las muestras de agua analizadas. Los resultados sugieren la existencia de un gradiente longitudinal en el contenido de toxinas directamente relacionado con el desarrollo de gradientes longitudinales de temperatura, salinidad y cocientes nutricionales a lo largo del estuario, e indirectamente relacionado con la turbidez del agua. Se observaron al menos cinco variantes de MC que se cuantificaron como equivalentes de MC-LR (Equiv. MC-LR). La concentración total de MC en material particulado varió de 0.0 a más de 1.0 μg Equiv. MC-LR·L-1, observándose siempre los valores superiores en la estación de agua dulce. Finalmente, fueron encontradas concentraciones de silicato disuelto en la columna de agua superiores a las de años anteriores. Estas diferencias reflejan cambios en el estado ecohidrológico del Guadiana probablemente relacionados con la construcción de la presa de Alqueva