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Interfacing PIC Microcontrollers 9

Interfacing PIC Microcontrollers 9. Explore in detail microcontroller interfacing techniques using the popular PIC 16F877 Work through step-by-step examples interactively using circuit simulation software, supplied as assembly source code Gain the knowledge of a wide range of peripheral devices such as keyboards, displays, sensors and drives and serial communication with other processors, memory and more Use interactive simulation software to design and test circuits. | Interfacing PIC Microcontrollers Figure 3.7 Watch window Ammeters. The complete list of tools available and how to use them is provided in the Proteus VSM help files. Meters Voltmeters and ammeters may be added to the circuit to measure volt drop across a component or absolute voltage at a point relative to 0 V Figure 3.8 . The ammeter measures current through a component or along a wire . As an example the current and voltage around one of the LEDs is shown with the LED on. The range and other properties of a meter can be changed by rightclicking on the instrument. Oscilloscope A virtual oscilloscope allows signals to be displayed in the same way as a real oscilloscope. Select it from the Instruments list and left-click to drop the 66 Circuit Simulation Figure 3.8 Voltmeter and ammeter minimised version on the drawing. Two channels A and B are available for connection to different points in the circuit with the 0 V being implicit. A larger display version is enabled by pausing the simulation and selecting the oscilloscope in the Debug menu. It is not displayed until the program is run with a signal in view the scope controls may be adjusted to obtain the best display and measure signal amplitude or frequency. Figure 3.9 shows the BIN4 application with a scope and logic analyser attached. A special version of the program with the delay commented out to speed it up was used to give a suitable scope display BIN4F . Figure 3.10 shows the clock output CLKOUT from the PIC chip alongside the LSB output at RB0 CLKOUT has to be enabled in the MCU Properties Advanced Properties dialogue . Logic Analyser The logic analyser allows multiple digital signals to be displayed simultaneously. They are captured by sampling a set of lines at regular intervals and storing the samples as binary bits. A typical mid-range analyser might have 48 inputs sampled at 25 MHz. Thus 6 bytes are stored every 40 p.s continuously. Unlike the oscilloscope when the analyser is triggered the data from