Data Bus Circuit

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 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 RTDvalue, in this case 1 kWthat results in an acceptable response time. The larger the RTD, the longer the response time...

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...

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...

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...

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...

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 device (when disabled by the bus controller) isolates access to the bus and minimizes capacitance loading. Additionally, PI3B16861s 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...

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.)..