formula.cpp

// This file contains code from NVSim, (c) 2012-2013,  Pennsylvania State University 
//and Hewlett-Packard Company. See LICENSE_NVSim file in the top-level directory.
//No part of DESTINY Project, including this file, may be copied,
//modified, propagated, or distributed except according to the terms
//contained in the LICENSE file.

#include "formula.h"
#include "constant.h"
#include <stdlib.h>

bool isPow2(int n) {
	if (n < 1)
		return false;
	return !(n & (n - 1));
}

double CalculateGateCap(double width, Technology tech) {
	return (tech.capIdealGate + tech.capOverlap + 3 * tech.capFringe) * width
			+ tech.phyGateLength * tech.capPolywire;
}

double CalculateFBRAMGateCap(double width, double thicknessFactor, Technology tech) {
	return (tech.capIdealGate / thicknessFactor + tech.capOverlap + 3 * tech.capFringe) * width
			+ tech.phyGateLength * tech.capPolywire;
}

double CalculateFBRAMDrainCap(double width, Technology tech) {
	return (3 * tech.capSidewall + tech.capDrainToChannel) * width;
}

double CalculateGateArea(
		int gateType, int numInput,
		double widthNMOS, double widthPMOS,
		double heightTransistorRegion, Technology tech,
		double *height, double *width) {
	double	ratio = widthPMOS / (widthPMOS + widthNMOS);

	double maxWidthPMOS, maxWidthNMOS;
	double unitWidthRegionP, unitWidthRegionN;
	double widthRegionP, widthRegionN;
	double heightRegionP, heightRegionN;

	if (ratio == 0) {	/* no PMOS */
		maxWidthPMOS = 0;
		maxWidthNMOS = heightTransistorRegion;
	} else if (ratio == 1) {	/* no NMOS */
		maxWidthPMOS = heightTransistorRegion;
		maxWidthNMOS = 0;
	} else {
		maxWidthPMOS = ratio * (heightTransistorRegion - MIN_GAP_BET_P_AND_N_DIFFS * tech.featureSize);
		maxWidthNMOS = maxWidthPMOS / ratio * (1 - ratio);
	}

	if (widthPMOS > 0) {
		if (widthPMOS < maxWidthPMOS) { /* No folding */
			unitWidthRegionP = tech.featureSize;
			heightRegionP = widthPMOS;
		} else {	/* Folding */
			int numFoldedPMOS = (int)(ceil(widthPMOS / (maxWidthPMOS - 3 * tech.featureSize)));	/* 3F for folding overhead */
			unitWidthRegionP = numFoldedPMOS * tech.featureSize + (numFoldedPMOS-1) * tech.featureSize * MIN_GAP_BET_POLY;
			heightRegionP = maxWidthPMOS;
		}
	} else {
		unitWidthRegionP = 0;
		heightRegionP = 0;
	}

	if (widthNMOS > 0) {
		if (widthNMOS < maxWidthNMOS) { /* No folding */
			unitWidthRegionN = tech.featureSize;
			heightRegionN = widthNMOS;
		} else {	/* Folding */
			int numFoldedNMOS = (int)(ceil(widthNMOS / (maxWidthNMOS - 3 * tech.featureSize)));	/* 3F for folding overhead */
			unitWidthRegionN = numFoldedNMOS * tech.featureSize + (numFoldedNMOS-1) * tech.featureSize * MIN_GAP_BET_POLY;
			heightRegionN = maxWidthNMOS;
		}
	} else {
		unitWidthRegionN = 0;
		heightRegionN = 0;
	}

	switch (gateType) {
	case INV:
		widthRegionP = 2 * tech.featureSize * (CONTACT_SIZE + MIN_GAP_BET_CONTACT_POLY * 2) + unitWidthRegionP;
		widthRegionN = 2 * tech.featureSize * (CONTACT_SIZE + MIN_GAP_BET_CONTACT_POLY * 2) + unitWidthRegionN;
		break;
	case NOR:
		widthRegionP = 2 * tech.featureSize * (CONTACT_SIZE + MIN_GAP_BET_CONTACT_POLY * 2)
						+ unitWidthRegionP * numInput + (numInput - 1) * tech.featureSize * MIN_GAP_BET_POLY;
		widthRegionN = 2 * tech.featureSize * (CONTACT_SIZE + MIN_GAP_BET_CONTACT_POLY * 2)
						+ unitWidthRegionN * numInput
						+ (numInput - 1) * tech.featureSize * (CONTACT_SIZE + MIN_GAP_BET_CONTACT_POLY * 2);
		break;
	case NAND:
		widthRegionN = 2 * tech.featureSize * (CONTACT_SIZE + MIN_GAP_BET_CONTACT_POLY * 2)
						+ unitWidthRegionN * numInput + (numInput - 1) * tech.featureSize * MIN_GAP_BET_POLY;
		widthRegionP = 2 * tech.featureSize * (CONTACT_SIZE + MIN_GAP_BET_CONTACT_POLY * 2)
						+ unitWidthRegionP * numInput
						+ (numInput - 1) * tech.featureSize * (CONTACT_SIZE + MIN_GAP_BET_CONTACT_POLY * 2);
		break;
	default:
		widthRegionN = widthRegionP = 0;
	}

	*width = MAX(widthRegionN, widthRegionP);
	if (widthPMOS > 0 && widthNMOS > 0) {	/* it is a gate */
		*height = heightRegionN + heightRegionP + tech.featureSize * MIN_GAP_BET_P_AND_N_DIFFS
					+ 2 * tech.featureSize * MIN_WIDTH_POWER_RAIL;
	} else {	/* it is a transistor */
		*height = heightRegionN + heightRegionP;	/* one of them is zero, and no power rail is added */
	}

	return (*width)*(*height);
}

void CalculateGateCapacitance(
		int gateType, int numInput,
		double widthNMOS, double widthPMOS,
		double heightTransistorRegion, Technology tech,
		double *capInput, double *capOutput) {
	/* TO-DO: most parts of this function is the same of CalculateGateArea,
	 * perhaps they will be combined in future
	 */
	double	ratio = widthPMOS / (widthPMOS + widthNMOS);

	double maxWidthPMOS = 0, maxWidthNMOS = 0;
	double unitWidthDrainP = 0, unitWidthDrainN = 0;
	double widthDrainP = 0, widthDrainN = 0;
	double heightDrainP = 0, heightDrainN = 0;
	int numFoldedPMOS = 1, numFoldedNMOS = 1;

	if (ratio == 0) {	/* no PMOS */
		maxWidthPMOS = 0;
		maxWidthNMOS = heightTransistorRegion;
	} else if (ratio == 1) {	/* no NMOS */
		maxWidthPMOS = heightTransistorRegion;
		maxWidthNMOS = 0;
	} else {
		maxWidthPMOS = ratio * (heightTransistorRegion - MIN_GAP_BET_P_AND_N_DIFFS * tech.featureSize);
		maxWidthNMOS = maxWidthPMOS / ratio * (1 - ratio);
	}

	if (widthPMOS > 0) {
		if (widthPMOS < maxWidthPMOS) { /* No folding */
			unitWidthDrainP = 0;
			heightDrainP = widthPMOS;
		} else {	/* Folding */
			if (maxWidthPMOS < 3 * tech.featureSize) {
				cout << "Error: Unable to do PMOS folding because PMOS size limitation is less than 3F!" <<endl;
				exit(-1);
			}
			numFoldedPMOS = (int)(ceil(widthPMOS / (maxWidthPMOS - 3 * tech.featureSize)));	/* 3F for folding overhead */
			unitWidthDrainP = (numFoldedPMOS-1) * tech.featureSize * MIN_GAP_BET_POLY;
			heightDrainP = maxWidthPMOS;
		}
	} else {
		unitWidthDrainP = 0;
		heightDrainP = 0;
	}

	if (widthNMOS > 0) {
		if (widthNMOS < maxWidthNMOS) { /* No folding */
			unitWidthDrainN = 0;
			heightDrainN = widthNMOS;
		} else {	/* Folding */
			if (maxWidthNMOS < 3 * tech.featureSize) {
				cout << "Error: Unable to do NMOS folding because NMOS size limitation is less than 3F!" <<endl;
				exit(-1);
			}
			numFoldedNMOS = (int)(ceil(widthNMOS / (maxWidthNMOS - 3 * tech.featureSize)));	/* 3F for folding overhead */
			unitWidthDrainN = (numFoldedNMOS-1) * tech.featureSize * MIN_GAP_BET_POLY;
			heightDrainN = maxWidthNMOS;
		}
	} else {
		unitWidthDrainN = 0;
		heightDrainN = 0;
	}

	switch (gateType) {
	case INV:
		if (widthPMOS > 0)
			widthDrainP = tech.featureSize * (CONTACT_SIZE + MIN_GAP_BET_CONTACT_POLY * 2) + unitWidthDrainP;
		if (widthNMOS > 0)
			widthDrainN = tech.featureSize * (CONTACT_SIZE + MIN_GAP_BET_CONTACT_POLY * 2) + unitWidthDrainN;
		break;
	case NOR:
		/* PMOS is in series, worst case capacitance is below */
		if (widthPMOS > 0)
			widthDrainP = tech.featureSize * (CONTACT_SIZE + MIN_GAP_BET_CONTACT_POLY * 2)
						+ unitWidthDrainP * numInput + (numInput - 1) * tech.featureSize * MIN_GAP_BET_POLY;
		/* NMOS is parallel, capacitance is multiplied as below */
		if (widthNMOS > 0)
			widthDrainN = (tech.featureSize * (CONTACT_SIZE + MIN_GAP_BET_CONTACT_POLY * 2)
						+ unitWidthDrainN) * numInput;
		break;
	case NAND:
		/* NMOS is in series, worst case capacitance is below */
		if (widthNMOS > 0)
			widthDrainN = tech.featureSize * (CONTACT_SIZE + MIN_GAP_BET_CONTACT_POLY * 2)
						+ unitWidthDrainN * numInput + (numInput - 1) * tech.featureSize * MIN_GAP_BET_POLY;
		/* PMOS is parallel, capacitance is multiplied as below */
		if (widthPMOS > 0)
			widthDrainP = (tech.featureSize * (CONTACT_SIZE + MIN_GAP_BET_CONTACT_POLY * 2)
						+ unitWidthDrainP) * numInput;
		break;
	default:
		widthDrainN = widthDrainP = 0;
	}

	/* Junction capacitance */
	double capDrainBottomN = widthDrainN * heightDrainN * tech.capJunction;
	double capDrainBottomP = widthDrainP * heightDrainP * tech.capJunction;

	/* Sidewall capacitance */
	double capDrainSidewallN, capDrainSidewallP;
	if (numFoldedNMOS % 2 == 0)
		capDrainSidewallN = 2 * widthDrainN * tech.capSidewall;
	else
		capDrainSidewallN = (2 * widthDrainN + heightDrainN) * tech.capSidewall;
	if (numFoldedPMOS % 2 == 0)
		capDrainSidewallP = 2 * widthDrainP * tech.capSidewall;
	else
		capDrainSidewallP = (2* widthDrainP + heightDrainP) * tech.capSidewall;

	/* Drain to channel capacitance */
	double capDrainToChannelN = numFoldedNMOS * heightDrainN * tech.capDrainToChannel;
	double capDrainToChannelP = numFoldedPMOS * heightDrainP * tech.capDrainToChannel;

	if (capOutput)
		*(capOutput) = capDrainBottomN + capDrainBottomP + capDrainSidewallN + capDrainSidewallP + capDrainToChannelN + capDrainToChannelP;
	if (capInput)
		*(capInput) = CalculateGateCap(widthNMOS, tech) + CalculateGateCap(widthPMOS, tech);
}

double CalculateDrainCap(
		double width, int type,
		double heightTransistorRegion, Technology tech) {
	double drainCap = 0;
	if (type == NMOS)
		CalculateGateCapacitance(INV, 1, width, 0, heightTransistorRegion, tech, NULL, &drainCap);
	else
		CalculateGateCapacitance(INV, 1, 0, width, heightTransistorRegion, tech, NULL, &drainCap);
	return drainCap;
}

double CalculateGateLeakage(
		int gateType, int numInput,
		double widthNMOS, double widthPMOS,
		double temperature, Technology tech) {
	int tempIndex = (int)temperature - 300;
	if ((tempIndex > 100) || (tempIndex < 0)) {
		cout<<"Error: Temperature is out of range"<<endl;
		exit(-1);
	}
	double *leakN = tech.currentOffNmos;
	double *leakP = tech.currentOffPmos;
	double leakageN, leakageP;
	switch (gateType) {
	case INV:
		leakageN = widthNMOS * leakN[tempIndex];
		leakageP = widthPMOS * leakP[tempIndex];
		return MAX(leakageN, leakageP);
	case NOR:
		leakageN = widthNMOS * leakN[tempIndex] * numInput;
		if (numInput == 2) {
			return AVG_RATIO_LEAK_2INPUT_NOR * leakageN;
		}
		else {
			return AVG_RATIO_LEAK_3INPUT_NOR * leakageN;
		}
	case NAND:
		leakageP = widthPMOS * leakP[tempIndex] * numInput;
		if (numInput == 2) {
			return AVG_RATIO_LEAK_2INPUT_NAND * leakageP;
		}
		else {
			return AVG_RATIO_LEAK_3INPUT_NAND * leakageP;
		}
	default:
		return 0.0;
	}
}

double CalculateOnResistance(double width, int type, double temperature, Technology tech) {
	double r;
	int tempIndex = (int)temperature - 300;
	if ((tempIndex > 100) || (tempIndex < 0)) {
		cout<<"Error: Temperature is out of range"<<endl;
		exit(-1);
	}
	if (type == NMOS)
		r = tech.effectiveResistanceMultiplier * tech.vdd / (tech.currentOnNmos[tempIndex] * width);
	else
		r = tech.effectiveResistanceMultiplier * tech.vdd / (tech.currentOnPmos[tempIndex] * width);
	return r;
}

double CalculateTransconductance(double width, int type, Technology tech) {
	double gm;
	double vsat;
	if (type == NMOS) {
		vsat = MIN(tech.vdsatNmos, tech.vdd - tech.vth);
		gm = (tech.effectiveElectronMobility * tech.capOx) / 2 * width / tech.phyGateLength * vsat;
	} else {
		vsat = MIN(tech.vdsatPmos, tech.vdd - tech.vth);
		gm = (tech.effectiveHoleMobility * tech.capOx) / 2 * width / tech.phyGateLength * vsat;
	}
	return gm;
}

double horowitz(double tr, double beta, double rampInput, double *rampOutput) {
	double alpha;
	alpha = 1 / rampInput / tr;
	double vs = 0.5;	/* Normalized switching voltage */
	double result = tr * sqrt(log(vs) * log(vs) + 2 * alpha * beta * (1 - vs));
	if (rampOutput)
		*rampOutput = (1 - vs) / result;
	return result;
}

double CalculateWireResistance(
		double resistivity, double wireWidth, double wireThickness,
		double barrierThickness, double dishingThickness, double alphaScatter) {
	return(alphaScatter * resistivity / (wireThickness - barrierThickness - dishingThickness)
			/ (wireWidth - 2 * barrierThickness));
}

double CalculateWireCapacitance(
		double permittivity, double wireWidth, double wireThickness, double wireSpacing,
		double ildThickness, double millerValue, double horizontalDielectric,
		double verticalDielectric, double fringeCap) {
	double verticalCap, sidewallCap;
	verticalCap = 2 * permittivity * verticalDielectric * wireWidth / ildThickness;
	sidewallCap = 2 * permittivity * millerValue * horizontalDielectric * wireThickness / wireSpacing;
	return (verticalCap + sidewallCap + fringeCap);
}