Presentation on theme: "EET 1131 Unit 6 Exclusive-OR and Exclusive-NOR Gates Read Kleitz, Chapter 6. Do Unit 6 e-Lesson. Homework #6 and Lab #6 due next week. Quiz next."— Presentation transcript:
EET 1131 Unit 6 Exclusive-OR and Exclusive-NOR Gates Read Kleitz, Chapter 6. Do Unit 6 e-Lesson. Homework #6 and Lab #6 due next week. Quiz next week.
Applications of XOR and XNOR Gates Three common applications: 1. Comparators 2. Controlled inverters 3. Parity generation and checking
Convention for Multi-Bit Strings When dealing with multi-bit binary strings, we use subscripts to refer to the individual bits in the string. The least significant bit (LSB) always gets the smallest subscript, which may be either 1 or 0. Example: In a four-bit string A, the bits may be labeled either A 4 A 3 A 2 A 1 or A 3 A 2 A 1 A 0
Application #1: Comparator A comparator compares two strings of bits to see whether they are equal to each other: Example: if string A = 0101 and string B = 0100, then A≠ B. Next slide shows how to build a 4-bit comparator from XNOR gates.
Application #2: Controlled Inverter A controlled inverter takes an input string and, depending on the logic level on a control line, either Leaves the string unchanged or Inverts each bit in the string Next slide shows how to build an 8-bit controlled inverter from XOR gates.
Parity Generators To implement parity checking, we need circuitry on the sending end that generates the parity bit for each group of bits being sent. This circuitry is called a parity generator. Next slide shows how to build 4-bit even or odd parity generators.
Parity Checkers On the receiving end, we need circuitry that checks the data bits and parity bit as they’re received to decide whether an error has occurred during transmission. This circuitry is called a parity checker. Next slide shows how to build a 4- bit-plus-parity even parity checker.
A Parity Generator/Checker Chip 74280 Nine-bit Parity Generator/Checker 74280 Most chips we’ve studied have been SSI (small-scale integration) chips containing fewer than 10 gates that are not connected to each other. The 74280 is an MSI (medium-scale integration) chip. Instead of containing a few disconnected gates, it contains about 45 gates connected internally on the chip to perform a specific function.
Printing from Our Oscilloscopes You can print the oscilloscope screen by pressing the PRINT button. There’s a delay of about 40 seconds before the page will print, so be patient. Only one oscilloscope can print at a time, or else the printer gets confused and prints hundreds of pages. Please shout “Printing!” before you press the PRINT button, and make sure that you don’t print while someone else is waiting for their page to print.