Data Bus Circuits

In the example, the PI3B16233 is a bidirectional device and can be easily controlled to convert from one format to the other. Given a double word that is located on the input of the A ports, the PI3B16233 can Mux the word over the B side in the desired order (see Figure 2.)

The device (when disabled by the bus controller) isolates access to the bus and minimizes capacitance loading. Additionally, PI3B16861’s flow-through pinout makes it ideal for board mounting and routing. Alternatively, the PI3B16215 can be used in applications where its B port prebiasing can minimize hot-insertion noise. Also, the low switch propagation delay (Tpd = 0.25ns) adds no appreciable delays into the system.

Migrating Applications to USB from RS-232 UART with Minimal Impact on PC Software

These peripherals are, in some instances, self-powered. As a result, many of these peripherals do not take full advantage of the USB port. Often overshadowed by the data interface is the power capability that a USB port provides. Microchip's MCP73853/55 and MCP73861 advanced, fully-integrated, single-cell Li-Ion/Li-Polymer charge-management devices allow these peripherals to utilize the full ?power? of the USB port.

Figure 1 illustrates the simplified block diagram of a typical high-speed data converter system. The system consists of a bandpass filter, ADC, high-frequency clock, high-speed storage device, and post processing unit. Aside from the MAX104, the high-frequency clock plays a significant role in determining the accuracy of a high-speed data converter. This high frequency, low-phase-noise clock is a combination of a high frequency voltage-controlled oscillator (U1), a phase-locked loop (U2), and a crystal oscillator (U3) as shown in Figure 2.

The design in Figure 1 is a visible optical link for those who need to see the transmitted data. An isolation figure of more than 5000V is a bonus. Tests of the system used the COM input of a data-acquisition system, as well as a standard PC's COM port. The MC1489 converts the RS-232C data to TTL signals. A 7404 gate then inverts the signal. The output of the 7404 drives Q1, a 2N3055 power transistor.

This Design Idea stems from the limited availability of IC voltage regulators that can meet key USB-power specs, coupled with the need for turn-on sequencing and rise-time control at each output. As always, for PC-related designs, minimum cost is a primary motivation. USB specs require all loads to limit inrush current to less than 100 mA plus 50 µC of charge when powered on. If permission is granted to increase the load to 500 mA, inrush limiting may be required again to prevent excursions over the 500-mA limit.

This application note illustrates the simple resistor network required for interfacing a PECL driver and an LVDS receiver. Both PECL and LVDS buffers implement differential low-voltage signaling techniques, but with different swing and offset voltage levels. A PECL driver’s differential output signal is more positive than is expected by the input circuit of an LVDS receiver. Implementing pulldown resistors in a Thevenin parallel termination resistor divider network will properly bias the PECL DC voltage level to within range of the LVDS receiver.

Another method that helps program development besides a dot LED as the output device is a serial bit. With a serial transmission to a terminal emulator program, developer may then test program running easier than a dot LED. One of my circuit uses PIC16F84 having one bit for sending ascii character with "printf" function. The PIC16F84 provides a very convenient way of connecting serial data to terminal. We may use a 1K resistor connects RB1, say to RxD pin of COM1 directly. As shown above diagram, my PIC circuit uses a transformerless DC supply. Direct connection is then not recommended for safety. The ground voltage difference between two circuits may destroy the RS232 converter chips.

Multiport RS-232C PC add-on boards are intended for intensive multichannel communication. Therefore, each serial port has its own transmission controller. If your application doesn't need interrupt-driven service, and polling the devices through RS-232C channels one after another is sufficient, then you can use a single controller with switched input and output signals instead of installing a costly multiport adapter.

The circuit in Figure 1 eliminates error by using a general-purpose amplifier and Kelvin-connected voltage references. The circuit also allows for single-supply operation and can detect temperatures of –200 to +400°C with an output-voltage-scaling factor (sensitivity) of 5 mV/°C. To reduce errors due to self-heating, the circuit uses the largest RTD—value, in this case 1 kW—that results in an acceptable response time. The larger the RTD, the longer the response time.

The method in Figure 1a needs no access or knowledge of the communicating devices. A C program opens two COM ports and installs interrupt-service routines for IRQ4 and IRQ3. Upon the reception of an interrupt, the routine stores a byte in a common circular buffer with the COM identifier and error flags. The main program displays the contents of the buffer, indicating time intervals in milliseconds between consecutive transfers. Although the program simplifies the time measurement, it preserves the original byte order and correctly reflects time relationships as long as the main program keeps up with transmission speed.

The circuit consists of two sections, one being a DC/DC converter and the other being a pair of dual N-channel MOSFETs and their associated high-side drivers that effectively form a DPDT switch.

The rapid, widespread use of 3.3V logic circuits complicates the selection of RS232 interface circuits. The optimum choice of an interface circuit should be based upon several application dependent factors: 1) Logic circuitry connected to interface chip 2) Power supply voltages available 3) Power consumption constraints 4) Serial interface environment 5) Mouse driving requirements

I will present the project in 2 sections: the first is a full-duplex transceiver, and the second is a transmitter only. The main reason for separating the design is to offer a cheaper solution if only half-duplex communication is required. For full-duplex communication 2 transceivers and 2 lasers will be required, and for half-duplex communication a single laser, a transmitter and a transceiver is needed. The transmitter can be also used as a stand-alone circuit if you only want to control the laser in other laser experiments.

Temperature measurements using RTDs (resistance-temperature detectors) generally employ bridge circuits with stable power supplies for signal conditioning. Unfortunately, this scheme generally produces nonlinear outputs. A linear bridge configuration that uses two identical current sources depends on the accuracy of matching the sources.

High speed data transmission requires a designer to be aware of factors which may impact the correct sampling of data. In particular, items such as excessive skew and jitter can lead to data sampling errors, limiting the maximum bandwidth performance of the LVDS Link. The following is a discussion of LVDS Link receiver data sampling, skew and jitter margin, and an explanation of skew and jitter components.

The intent of this application note is to provide the design engineer with a comprehensive guide to the implementation of the systems employing CAN products from National Semiconductor. The integrated programmable CAN interface block is available within the microcontrollers COP884BC and COP888EB. Additionally National provides a software which support a SLIO-CAN application based on the COP884BC.

LVDS (Low Voltage Differential Signaling) is a high speed general purpose interface that can be used in a wide range of application areas. Due to its small signal swing, differential signaling and current mode driver outputs, noise is minimized and very low power consumption across frequency is obtained.

The purpose of this application note is to provide the data mapping to ensure interoperability between the LVDS display interface (DS90C387/DS90CF388 chipset) and 18-bit or 24-bit FPD-Link devices. This data mapping must be used, so that the most significant bits (MSB) for an 18-bit application are mapped exactly the same as the most significant bits in the 24-bit application from the VGA controllers.