Serial Data Transfer (USART) 8251

UNIT IV

Chapter - 11

(d) Serial Data Transfer (USART) 8251

Contents

11.1 Serial Communication Supported by 8085 ... May-16 ….. Marks 8

11.2 Features of 8251A (USART) ….. May-04,  Dec.-05  …..Marks 5

11.3 Pin Diagram of 8251A

11.4 Block Diagram  ….. Dec.-07, ….. May-08,10, 11,13,16 …. Marks 16

11.5 8251A Control Words … Dec.-07

11.6 8251A Status Word        … Dec.-07  … Marks 8

11.7 Data Communication Types …. May-04, 05,        … Dec.-07 …. Marks   6

11.8 Interfacing 8251A in I/O Mapped I/O … May-12 … Marks 8

11.9 Programming 8251A  … May-10,11 … Marks 16

11.10 Two Marks Questions with Answers

11.11 University Questions with Answers (Long Answered Questions)

Most of the microprocessors are designed for parallel communication. In parallel communication number of lines required to transfer data depend on the number of bits to be transferred. For example, to transfer a byte of data, 8 lines are required and all 8 bits are transferred simultaneously. Thus for transmitting data over a long distance, using parallel communication is impractical due to the increase in cost of cabling. Parallel communication is also not practical for devices such as cassette tapes or a CRT terminal. In such situations, serial communication is used. In serial communication one bit is transferred at a time over a single line.