The PCA9548A is an octal bidirectional translating switch controlled via the I2C-bus. TheSCL/SDA upstream pair fans out to eight downstream pairs, or channels. Any individualSCx/SDx channel or combination of channels can be selected, determined by thecontents of the programmable control register.An active LOW reset input allows the PCA9548A to recover from a situation where one ofthe downstream I2C-buses is stuck in a LOW state. Pulling the RESET pin LOW resets theI2C-bus state machine and causes all the channels to be deselected as does the internalPower-on reset function.
上传时间： 2013-10-13
上传用户：bakdesec
The Philips family of Multiplexers and Switches consists of bi-directional translating switches controlled via the I2C or SMBus to fan out an upstream SCL/SDA pair to 2, 4 or 8 downstream channels of SCx/SDx pairs. The Multiplexers allow only one downstream channel to be selected at a time, while the Switches allow any individual downstream channel or combination of downstream channels to be selected, depending on the content of the programmable control register. Once one or several channels have been selected, the device acts as a wire, allowing the master on the upstream channel to send commands to devices on all the active downstream channels, and devices on the active downstream channels to communicate with each other and the master. External pull-up resistors are used to pull each individual channel up to the desired voltage level. Combined interrupt output and hardware reset input are device options that are featured.
上传时间： 2013-10-11
上传用户：dianxin61
Designing Boards with Atmel AT89C51, AT89C52, AT89C1051, and AT89C2051 for Writing Flash at In-Circuit Test:Recent improvements in chips andtesters have made it possible for thetester to begin taking over the role traditionallyassigned to the PROM programmer.Instead of having a PROM programmerwrite nonvolatile memoriesbefore assembling the board, the in-circuittester writes them during in-circuittesting operations. Many Teradyne Z18-series testers are now in use loadingcode into nonvolatile memories, microcontrollersand in-circuit programmable logic devices. The purpose of this note is to explain how the Z18 approaches the writing task for Atmel AT89C series IC’s,so that designers of boards using these chips can get the best results.
标签： Designing Boards Atmel with
上传时间： 2013-11-20
上传用户：lijianyu172
基于单片机的LED汉字显示屏设计与制作：在大型商场、车站、码头、地铁站以及各类办事窗口等越来越多的场所需要用LED点阵显示图形和汉字。LED行业已成为一个快速发展的新兴产业，市场空间巨大，前景广阔。随着信息产业的高速发展，LED显示作为信息传播的一种重要手段，已广泛应用于室内外需要进行服务内容和服务宗旨宣传的公众场所，例如户内外公共场所广告宣传、机场车站旅客引导信息、公交车辆报站系统、证券与银行信息显示、餐馆报价信息豆示、高速公路可变情报板、体育场馆比赛转播、楼宇灯饰、交通信号灯、景观照明等。显然，LED显示已成为城市亮化、现代化和信息化社会的一个重要标志。 本文基于单片机(AT89C51)讲述了16×16 LED汉字点阵显示的基本原理、硬件组成与设计、程序编译与下载等基本环节和相关技术。2 硬件电路组成及工作原理本产品拟采用以AT89C51单片机为核心芯片的电路来实现，主要由AT89C51芯片、时钟电路、复位电路、列扫描驱动电路(74HC154)、16×16 LED点阵5部分组成，如图1所示。 其中，AT89C51是一种带4 kB闪烁可编程可擦除只读存储器(Falsh programmable and Erasable Read OnlyMemory，FPEROM)的低电压、高性能CMOS型8位微处理器，俗称单片机。该器件采用ATMEL高密度非易失存储器制造技术制造，与工业标准的MCS-51指令集和输出管脚相兼容。由于将多功能8位CPU和闪烁存储器组合在单个芯片中，能够进行1 000次写／擦循环，数据保留时间为10年。他是一种高效微控制器，为很多嵌入式控制系统提供了一种灵活性高且价廉的方案。因此，在智能化电子设计与制作过程中经常用到AT89C51芯片。时钟电路由AT89C51的18，19脚的时钟端(XTALl及XTAL2)以及12 MHz晶振X1、电容C2，C3组成，采用片内振荡方式。复位电路采用简易的上电复位电路，主要由电阻R1，R2，电容C1，开关K1组成，分别接至AT89C51的RST复位输入端。LED点阵显示屏采用16×16共256个象素的点阵，通过万用表检测发光二极管的方法测试判断出该点阵的引脚分布，如图2所示。 我们把行列总线接在单片机的IO口，然后把上面分析到的扫描代码送人总线，就可以得到显示的汉字了。但是若将LED点阵的行列端口全部直接接入89S51单片机，则需要使用32条IO口，这样会造成IO资源的耗尽，系统也再无扩充的余地。因此，我们在实际应用中只是将LED点阵的16条行线直接接在P0口和P2口，至于列选扫描信号则是由4-16线译码器74HC154来选择控制，这样一来列选控制只使用了单片机的4个IO口，节约了很多IO资源，为单片机系统扩充使用功能提供了条件。考虑到P0口必需设置上拉电阻，我们采用4.7 kΩ排电阻作为上拉电阻。
上传时间： 2013-10-16
上传用户：ywcftc277
82C59A-2是为简化微处理机系统中断接口而实现的LSI外围芯片。也叫做PIC（programmable Interrupt Controller）。是高性能高速度芯片。在多级优先级中断系统内82C59A-1402已经把CPU从对任务的轮询中解救出来。PCI可由软件进行控制，使用于各种不同的环境，联级可接受8~64个中断输入。 管脚与NMOS8259A-2兼容单片8级优先级，级联可扩64级多种可编程中断方式各自专用的请求屏蔽能力与Intel系列机兼容全部采用静态设计低功耗5V的电源供电。
上传时间： 2013-10-30
上传用户：zhliu007
The μPSD32xx family, from ST, consists of Flash programmable system devices with a 8032 MicrocontrollerCore. Of these, the μPSD3234A and μPSD3254A are notable for having a complete implementationof the USB hardware directly on the chip, complying with the Universal Serial Bus Specification, Revision1.1.This application note describes a demonstration program that has been written for the DK3200 hardwaredemonstration kit (incorporating a μPSD3234A device). It gives the user an idea of how simple it is to workwith the device, using the HID class as a ready-made device driver for the USB connection.IN-APPLICATION-PROGRAMMING (IAP) AND IN-SYSTEM-PROGRAMMING (ISP)Since the μPSD contains two independent Flash memory arrays, the Micro Controller Unit (MCU) can executecode from one memory while erasing and programming the other. Product firmware updates in thefield can be reliably performed over any communication channel (such as CAN, Ethernet, UART, J1850)using this unique architecture. For In-Application-Programming (IAP), all code is updated through theMCU. The main advantage for the user is that the firmware can be updated remotely. The target applicationruns and takes care on its own program code and data memory.IAP is not the only method to program the firmware in μPSD devices. They can also be programmed usingIn-System-Programming (ISP). A IEEE1149.1-compliant JTAG interface is included on the μPSD. Withthis, the entire device can be rapidly programmed while soldered to the circuit board (Main Flash memory,Secondary Boot Flash memory, the PLD, and all configuration areas). This requires no MCU participation.The MCU is completely bypassed. So, the μPSD can be programmed or reprogrammed any time, anywhere, even when completely uncommitted.Both methods take place with the device in its normal hardware environment, soldered to a printed circuitboard. The IAP method cannot be used without previous use of ISP, because IAP utilizes a small amountof resident code to receive the service commands, and to perform the desired operations.
标签： Demonstration 3200 USB for
上传时间： 2014-02-27
上传用户：zhangzhenyu
The μPSD32xx family, from ST, consists of Flash programmable system devices with a 8032 Microcontroller Core. Of these, the μPSD3234A and μPSD3254A are notable for having a complete implementation of the USB hardware directly on the chip, complying with the Universal Serial Bus Specification, Revision 1.1.This application note describes a demonstration program that has been written for the DK3200 hardware demonstration kit (incorporating a μPSD3234A device). It gives the user an idea of how simple it is to work with the device, using the HID class as a ready-made device driver for the USB connection.
上传时间： 2014-04-03
上传用户：lizhizheng88
I2C interface, is a very powerful tool for system designers. Theintegrated protocols allow systems to be completely software defined.Software development time of different products can be reduced byassembling a library of reusable software modules. In addition, themultimaster capability allows rapid testing and alignment ofend-products via external connections to an assembly-line computer.The mask programmable 87LPC76X and its EPROM version, the87LPC76X, can operate as a master or a slave device on the I2Csmall area network. In addition to the efficient interface to thededicated function ICs in the I2C family, the on-board interfacefacilities I/O and RAM expansion, access to EEPROM andprocessor-to-processor communications.
标签： microcontro Using 76X LPC
上传时间： 2013-12-30
上传用户：Artemis
The MC68HC05K0 is a low cost, low pin countsingle chip microcomputer with 504 bytes of userROM and 32 bytes of RAM. The MC68HC05K0 isa member of the 68HC05K series of devices whichare available in 16-pin DIL or SOIC packages.It uses the same CPU as the other devices in the68HC05 family and has the same instructions andregisters. Additionally, the device has a 15-stagemulti-function timer and 10 general purposebi-directional I/0 lines. A mask option is availablefor software programmable pull-downs on all ofthe I/O pins and four of the pins are capable ofgenerating interrupts.The device is ideally suited for remote-controlkeyboard applications because the pull-downs andthe interrupt drivers on the port pins allowkeyboards to be built without any externalcomponents except the keys themselves. There isno need for external pull-up or pull-down resistors,or diodes for wired-OR interrupts, as these featuresare already designed into the device.
上传时间： 2014-01-24
上传用户：zl5712176
The AT89C52 is a low-power, high-performance CMOS 8-bit microcomputer with 8Kbytes of Flash programmable and erasable read only memory (PEROM). The deviceis manufactured using Atmel’s high-density nonvolatile memory technology and iscompatible with the industry-standard 80C51 and 80C52 instruction set and pinout.The on-chip Flash allows the program memory to be reprogrammed in-system or by aconventional nonvolatile memory programmer. By combining a versatile 8-bit CPUwith Flash on a monolithic chip, the Atmel AT89C52 is a powerful microcomputerwhich provides a highly-flexible and cost-effective solution to many embedded controlapplications.
上传时间： 2013-11-10
上传用户：1427796291
