296617668-Asynchronous-Data-Transfer.ppt
- 1. CS-’A’ ASYNCHRONOUS DATA TRANSFER Guided By: Submitted By: Mrs. Rupali Bhartiya Navin Kumar Sharma Roll no.:0802CS143D02 SHRI VAISHNAV INSTITUTE OF TECHNOLOGY & SCIENCE, INDORE
- 2. INTRODUCTION
- 3. Introduction • Asynchronous data transfer between two independent units requires that control signals be transmitted between the communicating units to indicate the time at which data is being transmitted
- 4. Two Asynchronous Data Transfer Methods • Strobe pulse: • A strobe pulse is supplied by one unit to indicate the other unit when the transfer has to occur • Handshaking • A control signal is accompanied with each data being transmitted to indicate the presence of data The receiving unit responds with another control signal to acknowledge receipt of the data
- 5. STROBE CONTROL • Employs a single control line to time each transfer • The strobe may be activated by either the source or the destination unit
- 6. Source Unit Destination Unit Data bus Strobe Strobe Data Valid data a) Block diagram b) Timing diagram Source-Initiated Strobe for Data Transfer
- 7. Destination-Initiated Strobe for Data Transfer Source Unit Destination Unit Data bus Strobe Strobe Data Valid data a) Block diagram b) Timing diagram
- 8. HANDSHAKING • Strobe Methods • Source-Initiated • The source unit that initiates the transfer has no way of knowing whether the destination unit has actually received data • Destination-Initiated • The destination unit that initiates the transfer no way of knowing whether the source has actually placed the data on the bus • To solve this problem, the HANDSHAKE method introduces a second control signal to provide a Replay to the unit that initiates the transfer
- 9. SOURCE-INITIATED TRANSFER USING HANDSHAKE Block Diagram Source unit Destination unit Data valid Data bus Data accepted
- 10. Timing Diagram
- 12. • Allows arbitrary delays from one state to the next * Permits each unit to respond at its own data transfer rate * The rate of transfer is determined by the slower unit
- 13. DESTINATION-INITIATED TRANSFER USING HANDSHAKE Block Diagram Source unit Destination unit Data valid Data bus Ready for Data
- 14. Timing Diagram
- 16. ASYNCHRONOUS SERIAL TRANSFER • The transfer of data between two units my be done in parallel or serial. • In parallel data transmission, total message is transmitted at the same time. In serial data transmission, each bit in the message is sent in sequence one at a time. • In asynchronous transmission, binary information is sent only when it is available and the line remains idle when there is no information to be transmitted.
- 17. Start bit Stop bit Character bits 1 1 1 1 0 0 0 0 ASYNCHRONOUS SERIAL TRANSFER
- 18. • Asynchronous serial transmission is character oriented. • Each character transmitter consists of a start bit, character bits, and stop bits. The first bit is called the start bit. • It is always a 0 and is used to indicate the beginning of a character. The last bit called the stop bit is always a 1.