8051 microcontrollers

Test On Digital Electronics Applications Do not refer to the text when taking this test. You may draw diagrams or use a calculator if necessary. A good score is at least 38 correct answers. Answers are in the back of the book. It’s best to have a friend check your score the first time so you won’t memorize the answers if you want to take the test again. 1. A signal with a 100 ns time ‘‘On’’ and a 230 ns time ‘‘Off’’ has a frequency of: (a) 30.3% (b) 3 GHz (c) 3 MHz (d) 3 kHz 2. A toggle flip flop will divide a clock frequency by: (a) The value selected in its inputs (b) 2 (c) 1.5, but the output duty cycle is 50% (d) The toggle flip flop is used for debouncing switch inputs 3. The NPN transistor relaxation oscillator is well suited for: (a) High-speed computer applications (b) Only audio applications (c) Low-cost applications where accuracy isn’t important (d) Power supply duty cycle generators 4. If you wanted an oscillator that produced a period of 4 gate ...

Synchronous Serial Interfaces (SPI, I2C, Microwire) There are two very common synchronous data protocols, Microwire and SPI, from which a variety of standard devices (memory and peripheral functions) have been designed around, including serial EEPROMs, sensors and other I/O functions. I consider these protocols to be methods of transferring synchronous serial data rather than intelligent network protocols because each device is individually addressed (even though the clock/data lines can be common between multiple devices). If the chip select for the device is not asserted, the device ignores the clock and data lines. With these protocols, only a single ‘‘Master’’ can be on the bus. Normally, just eight bits of data are sent out at a time. For protocols like Microwire where a ‘‘Start bit’’ is initially sent, the ‘‘Start bit’’ is sent using direct reads and writes to the I/O pins. To receive data, a similar circuit would be used, but data would be shifted into the shift register and...

PC Interfacing Basics From a practical point of view, chances are you will be designing an interface or enhancement to your PC. Most modern commercial devices utilize USB ports, but you can still do a lot of interesting projects with the ‘‘legacy’’ interfaces built into the PC. Along with this, a basic understanding of your PC will help you understand how commercial products are designed and may give you some ideas as to how you can design your own complex applications. The PC ‘‘core’’ circuitry consists of the microprocessor, memory, the interrupt controller and a DMA controller, as shown in Fig. 13-1. This set of hardware can run any program or interface with hardware attached to this ‘‘local bus’’. While you may think of processor memory in terms of the megabytes that were advertised when you bought the PC, there are actually three different types of memory that are accessed. The term ‘‘local memory’’ is kind of a loosely defined term that I use to describe memory on the PC’s mo...

Power Supplies It is surprising to many people that you can add a simple voltage regulator to power your projects for just a few dollars; cheaper than a set of rechargeable batteries. Voltage regulators, powered by an AC/DC ‘‘Wall wart’’ power converter, will convert one DC voltage to another that can be used by the electronics in your circuit and, more importantly, will be tolerant of changes in the AC supply and the current load. In this section, I will introduce you to some simple power supply circuits that have the following characteristics: 1. They are safe for their users and designers. 2. They are relatively efficient in terms of the amount of power that is  lost converting voltage levels. 3. They provide very accurate voltage levels, independent of the voltage input or the current required by the application. 4. They are inexpensive. 5. Their design can be optimized for the application that they are providing power for. 6. These supplies source up to 1 amp o...