微机原理课件ch11英文.pptVIP

Used to convert between analog and digital data. For example, the DAC 0830 (National Semi Corp.) is an 8-bit DAC that transforms an 8-bit binary number to an analog voltage. 8-bit yields 256 different analog voltages. 10-bit, 12-bit and 16-bit are also available. Conversion time is 1μs. * 第*页 8-bit digital value drives D0 through D7. The outputs are IOUT1 and IOUT2. The output step voltage is defined by -VREF (reference voltage), divided by 255, e.g. if VREF = -5.0V, then the output step voltage is +0.0196. The output step voltage is called the resolution of the converter. * 第*页 The ADC0804 is an 8-bit analog-to-digital converter that requires up to 100us to convert an analog input voltage into a digital output. * 第*页 * 第*页 2,3,5,8,12,16,19,24 27,31,32,39 54,55,60 63,64 70,72,75 * 第*页 Example 11-8,9,10 * 第*页 Mode 0 operation causes the 82C55 to function as a buffered input device or as a latched output device. In previous example, both ports A and B are programmed as (mode 0) simple latched output ports. Port A provides the segment data inputs to display and port B provides a means of selecting one display position at a time. Different values are displayed in each digit via fast time multiplexing. The values for the resistors and the type of transistors used are determined using the current requirements (see text for details). Textbook has the assembly code fragment demonstrating its use. Examples of connecting LCD displays and stepper motors are also given. * 第*页 Three independent 16-bit programmable counters (timers). Each capable in of counting in binary or BCD with a maximum frequency of 10MHz. Used for controlling real-time events such as real-time clock, events counter, and motor speed and direction control. * 第*页 * 第*页 A1, A0?The address inputs select one of the four internal registers with the 8254 as follows: * 第*页 CLK?The clock input is the timing source for each of the internal counters. CS?Chip Select enables the 8254 for programming, and reading and wri