一种具有自校准、自控制功能的I2C接口电路

文章提出一种在开漏模式下通过硬件自检测、自校准实现高性能I²C(inter-integrated circuit)接口的设计，并给出一种I²C接口自控制实现开漏功能的方法。在传统I²C接口电路的基础上，增加了自检测拉低时钟总线并进行自校准的功能，使得在开漏模式下，硬件能够自动检测到时钟总线在上拉过程中的低电平并进行自校准高电平，在改善通信稳定性的基础上实现了性能提升。考虑到不同的应用场合，增加了开漏使能控制电路，为提高IP的可移植性，I²C接口可自控制开漏功能，支持软件配置，灵活地应用于各种通用输入输出(general-purpose input/output, GPIO)模型中。成品开发板电路测试表明，在系统时钟为120 MHz时，该电路在开漏模式下高速通信中的位速率高达5.98 Mbit/s,在推挽模式下超快速通信中的位速率高达30.00 Mbit/s。     

基于ZigBee无线传感器网络的温室监测系统设计

为了解决温室环境监测系统中遇到拓扑结构固定、节点延展性差等问题,提出了基于ZigBee无线传感器网络的温室监测系统设计与实现方法,构建了基于ZigBee协议的无线监测网络,给出了网络中节点硬件和软件的设计方案,详细论述了ZigBee协调器的组网过程。该系统利用PIC18F4620单片机控制CC2420无线收发器模块收发数据、驱动温湿度传感器（SHT11）,通过I²C总线方式进行数据采集,将采集的温湿度经ZigBee网络传输到监测平台。测试结果表明,该系统具有结构简单、节点灵活、功耗低等优点,实现了在无线环境下对温室中温湿度的有效监测。     

I~2C总线器件扩展单片机的接口

分析I2 C总线的优点 ,时序和数据传输格式 ,利用单片机的I/ 0口线模拟I2 C总线传输信息 ,以此来扩展单片机的I/ 0接口 .     

单主系统中I2C总线的虚拟技术

主要介绍在单主系统中，利用单片机的通用I／O口来虚拟I^2C总线接口，通过相应程序的设计，实现在无I^2C总线接口的单片机系统中扩展具有I^2C总线接口外围设备的目的。     

8051单片机系统I~2C总线接口设计与实现

介绍了I2C总线技术标准,结合8051单片机与24LC02B芯片之间组成的I2C总线,给出了硬件连接设计,并用Keil C51给出了8051在总线上读写数据过程的软件代码,阐明了8051单片机I2C总线接口的实现方法.     

多单片机公共总线系统及总线仲裁逻辑的GAL实现

讨论了公共总线多单片机系统,该系统由８０９６／８０５１单片机主模块、共享存储器、共享Ｉ／Ｏ、总线接口及仲裁器构成。重点分析了总线接口逻辑和判优逻辑及ＧＡＬ实现。     

基于CPLD的SAA7113的初始化及其控制设计

为了实现对视频图像的采集和多格式输出,通常使用低速存储器存储所采集的图像信息.笔者介绍了视频解码芯片SAA7113的特点及其应用,研究了基于CPLD对SA7113的硬件电路配置结构的实现,并给出了使用VHDL语言通过I²C总线进行初始化控制的编程方法,从而实现了视频采集和使用8 MHz/s的低速存储器存储所采集的图像信息,并能根据需要由多种格式输出.     

基于PIC18单片机的RS-232/RS-485/CAN互联适配器的设计

本文讨论了基于单片机实现CAN总线通信的方法,提出一种基于PIC18单片机实现RS-232接口、RS-485总线、CAN总线网络互联的方案。     

I2C总线及其在智能矿用管理仪的应用

串行扩展总线技术是新一代单片机技术发展的一个显著特点,其中Philips公司推出的I2C总线较为著名.文章介绍了I2C总线原理, I2C总线接口器件以及在智能矿用管理仪中的应用.给出了它的应用系统设计和软件编程.     

P89V51RD2与SJA1000实现CAN节点实例

介绍CAN总线控制器SJA1000与PHILIPS公司51系列单片机P89V51RD2实现CAN智能节点的接口方法,给出了CAN总线接口电路、SJA1000初始化的方法及简单收发的实现;对SJA1000在应用中容易出现的问题进行分析,并给出了解决方法。     

The features of microcontroller EM78P447 and technique of port connection with I2C series bus

By describing the technique of port connection and flow chart ofR/W operation between 24LC01, serial E²PROM, and EM78P447A, features of EM78P447 and its connection with I²C serial bus are introduced. In the end, the programe of writing operation is given. Foundations item: Research on Electromagnetic Scatter Character of very Complicate Object (69571021) Biography: Huang Ji-wu(1939-), male, Associate professor, research direction: control with microcomputer and intelligent system.     

Carbon isotopic composition,turnover and origins of soil CO<Subscript>2</Subscript> in a monsoon evergreen broadleaf forest in the Dinghushan Biosphere Reservoir,South China

Carbon isotopic compositions of soil CO2 in rainy season (July) from two natural soil profiles (DHLS & DHS) in the monsoon evergreen broadleaf forest in the Dinghushan Biosphere Reservoir (DBR), South China, are presented. Turnover and origins of soil CO₂ are preliminarily discussed in this paper. Results show that the content of soil CO2 varies between 6120 and 18718 ppmv, and increases with increasing depth until 75 cm, and then it declines. In DHLS, soil CO₂ δ¹³C ranges from −24.71‰ to −24.03‰, showing a significant inverse correlation (R²＝0.91) with the soil CO₂ content in the same layer. According to a model related to soil CO₂ δ¹³C, the soil CO₂ is mainly derived from the root respiration (>80%) in DHLS. While in DHS, where soil CO₂ ? 13C ranges from −25.19‰ to −22.82‰, soil CO₂ is primarily originated from the decomposition of organic matter (51%–94%), excluding the surface layer (20 cm, 90%). Radiocarbon data suggest that the carbon in soil CO₂ is modern carbon in both DHLS and DHS. Differences in ¹⁴C ages between the “oldest” and “youngest” soil CO₂ in DHLS and DHS are 8 months and 14 months, respectively, indicating that soil CO₂ in DHLS has a faster turnover rate than that in DHS. The ¹⁴C values of soil CO₂, which range between 100.0‰ and 107.2‰ and between 102.5‰ and 112.1‰ in DHLS and DHS, respectively, are obviously higher than those of current atmospheric CO₂ and SOC in the same layer, suggesting that soil CO₂ is likely an important reservoir for Bomb-¹⁴C in the atmosphere.     

Theoretical study of partial oxidation of ethylene by vanadium trioxide cluster cation

Density functional theory （DFT） study of reaction between vanadium trioxide cluster cation （VO3^＋） and ethylene （C2H4） to yield VO2^＋ ＋ CH3CHO （acetaldehyde） and VO2CH2^＋ ＋ HCHO （formaldehyde） is carried out. Structures of all reactants, products, intermediates, and transition state in the reaction have been optimized and characterized. The results show unexpected barriers in the reaction due to the existence of a η^2-O2 moiety in the ground state structure of VO3^＋. The initial reaction steps combining ethylene adsorption, C=C activation and O-O cleavage are proposed as rate limiting processes. Comparison of reactions of VO3^＋ ＋ C2H4 with VO3 ＋ C2H4 and VO2^＋ ＋ C2H4 in the previous studies is made in detail. The results of this work may shed light on the understanding of C=C bond cleavage in related heterogeneous catalysis.     

I-doping of anodized TiO<Subscript>2</Subscript> nanotubes using an electrochemical method

In order to obtain TiO2 with high photocatalytic activity, a cathode reduction was used to dope I⁷⁺ and I⁵⁺ into TiO₂ nanotubes of anodized Ti in C₂H₂O₄•2H₂O + NH₄F electrolyte. SEM images show that the anodization method integrated the preparation with the doping process, which for nonmetals-doping is advantageous to maintain the morphological integrity of TiO₂ nanotubes. I⁷⁺-I⁵⁺-doping enhances the UV response of TiO₂ and result in a red-shift. Under UV/visible irradiation, a I⁷⁺-I⁵⁺-doped sample (400°C) showed the highest I_ph and photocatalytic efficiency. A part of I^– in the I⁷⁺-I⁵⁺-doped sample is involved in the UV response, the red-shift and the higher I_ph.     

14C measurement of forest soils in Dinghushan Biosphere Reserve

Organic carbon in forest soils of Qingyunsi and Wukesong profiles can be divided into fast and slow components. Δ 14C values of these profiles decrease with increasing of depth. The Δ 14C values in 30-40 cm depth interval of Wukesong profile are decreasing sharply until a very low value, showing that a strong geological environment change occurred about 1 560 years ago. The 14C apparent ages of Wukesong profile show that the coniferous and broad-leaf mixed forests around Wukesong profile have been developing since 425 a BP, which is consistent with historical documents. The penetrating depths of "bomb 14C" in Qingyunsi and Wukesong profiles are 10 and 20 cm, respectively.     

Effect of MTEC1 on the functional expression of TCRaβ+ 3G11− 6C10− CD4+ CD8− thymocyte subset

A murine CD4⁺ thymocyte subset with phenotype of TCRαβ⁺ 3G11⁻ 6C10⁻ CD4⁺ CD8⁻ CD69^+/- HSA^med/lo contains the cells in relatively functional matured status. The functional property of the cells in this subset is characterized by the unique pattern of cytokine production at transitional stage from Th0 to Th2 type with the latter being the dominant type. After being co-cultured with murine thymic medullary epithelial cell line (MTEC1) cells, a murine thymic medullary type epithelial cell line, the TCRαβ⁺ 3G11⁻ 6C10⁻ CD4⁺ CD8⁻ CD69^+/- HSA^med/lo thymocytes, has exhibited significantly higher levels of proliferation capability and IL-6 production, whereas the production of IL-4 and IL-10 is suppressed after co-culturing with MTECl. By contrast, MTECl could not induce thymocytes to secrete Thl type of cytokines. The results suggest that MTECl can regulate functional status of this thymocyte subset and induce them to develop into a specialized Th2 subset.     

Phenotypic analysis of the medullary-type CD4−CD8+ thymocytes in mice

Phenotypic analysis of the medullary-type CD4 CD8⁺ (CD8SP) thymocytes has revealed phenotypic heterogeneity within this cell population. The phenotype of mature peripheral CDS⁺T cells is TCRαβ⁺CD3⁺Qa-2⁺HSA 3G11⁻6C10, whereas in the medullary-type CD8SP thymocytes, 20% are Qa-2⁺; 33%, HAS; 30%, 3G11; and 70% are 6C10. The disparate expression patterns of these four cell surface markers suggest that medullary-type CD8SP thymocytes may undergo phenotypic maturation process. According to the distribution of these four cell surface markers, six subgroups of CD8SP thymocytes have been identified. The precursor-progeny relationship along with developmental pathway is postulated as follows: 6C10⁺HSA⁺3G11 Qa-2→ 6C10⁺HSA⁺ 3G11⁺Qa-2 → 6C10 HSA⁺3G11⁺Qa-2 → 6C10⁻HSA⁻3G11⁺Qa-2 → 6C10⁻HSA⁻3G11 Qa-2 → 6C10⁻HA S 3G11 Qa-2⁺, the cells in the last subgroup exit the thymus and home into periphery.     

Carbon and nitrogen stable isotope analyses of mammal bone fossils from the Zhongba site in the Three Gorges Reservoir region of the Yangtze River,China

Based on AMS ¹⁴C dating data, carbon and nitrogen isotope analyses were conducted on mammal bone collagen of deer, cattle and pigs from the Zhongba site in the Three Gorges Reservoir region of the Yangtze River. These analyses were conducted to reconstruct palaeodiets of mammals, palaeoecology, palaeoenviroment and previous human activities in the study area. Results show that the collagen loss of bone did not change the in vivo isotopic composition of carbon and nitrogen stable isotopes, and most of the bone fossils were well preserved. The bone collagen of samples from deer had a mean δ¹³C of -23.1‰ and a mean δ¹⁵N of 4.7‰, suggesting that deer subsisted in a closed habitat and fed on branches and leaves. The bone collagen of cattle had a mean δ¹³C of –19.6‰ and a mean δ¹⁵N of 5.2‰, which indicates that cattle subsisted in an open habitat and fed on grasses and stems. The δ¹³C values show that both deer and cattle fed on C₃ plants and lived in the same ecosystem, but the t-test results show that deer δ¹³C and δ¹⁵N values were both more negative than those of cattle, indicating that they inhabited different niches. The δ¹³C and δ¹⁵N values of cattle partially overlapped those of deer, suggesting some competition in diets between them. The t-tests show that the δ¹³C and δ¹⁵N values of pigs were more positive than those of cattle and deer, which signifies that pigs occupied a higher trophic level compared to cattle and deer. The wide range of pig δ¹³C values demonstrates that pig trading had been taking place from early Neolithic Age to late Bronze Age. There were no significant differences in deer δ¹³C and δ¹⁵N values among different archaeological periods, making it clear that climatic, ecological and environmental conditions were kept relatively stable from 2200 to 4200 a BP. This stability may have been responsible for the extensive and complete cultural layers at the Zhongba site. The minimum number of samples required to estimate the mean δ¹³C values of deer, pigs and cattle are 8, 73 and 16, respectively, and for mean δ¹⁵N values of deer, pigs and cattle, the minimum numbers are 4, 5 and 6, respectively.     

Callus formation in relation to changes of the membrane Ca2+ in the graft unions ofGinkgo biloba L.

The relationship between the callus formation and intracellular Ca²⁺ at the early stage of development of graft unions inGinkgo biloba L. was investigated. On the second day after grafting, part of the undamaged living cells at the graft interface of the stock and scion in the regions of the cortex and pith began to dedifferentiate or divide. 8 d after grafting, a great number of callus cells were produced from the cortex and phloem, while callus bridges linking the stock with scion formed between the callus cells of the graft partners from the cortex. A membrane Ca²⁺ probe, chlortetracycline (CTC), was used to locate the intracellular Ca²⁺ distribution and it was found that the cortical and pith parenchyma cells were the first to show remarkably increased CTC-Ca²⁺ fluorescence, suggesting that the cortical and other parenchyma cells play a leading role at the early stage of development of graft unions by earlier dedifferentiation and more rapid production of callus cells.     

Export and remineralization of POM in the Southern Ocean and the South China Sea estimated from 210Po/210Pb disequilibria

Disequilibria between ^210Po and ^210Pb in the upper water and their potential applications as a proxy of particle export and remineralization were examined in the Southern Ocean （station IV3） and the South China Sea （NS44）. ^210po was deficit in surface waters but excessive relative to ^210Pb in subsurface waters. Good positive correlation between ^210Po and particulate organic carbon （POC） indicated deficits and excess of ^210Po resulted from particulate organic matter （POM） export and remJneralization respectively, which was also supported by the decreased δ^13C and increased δ^15N downwards as a result of particle remineralization. On the basis of ^210Po/^210Pb box-model, POC export flux out of the surface waters were 1.2 mmol C. m^-2. d^-1 and 2.3 mmol C. m^-2. d^-1 for station NS44 and IV3, respectively. In the subsurface waters, remineralization fluxes of ^210Po were 0.062 Bq. m^-2.d^-1 and 0.566 Bq.m^-2.d^-1 for station NS44 and IV3 along with the recycle efficiency of 52±26% and 119±52%, respectively. Remineralized fluxes of POM derived from ^210Po and exported POC were 0.6 mmol C.m^-2.d^-1 and 2.7 mmol C. m^-2. d^-1 for NS44 and IV3. This study suggested that ^210Po was a powerful tracer of particle export and remineralization.