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Data Communication Basics
This document discusses different methods of data communication between devices: simple I/O, strobe I/O, single handshake I/O, and double handshake I/O. Simple I/O involves a device constantly outputting data that is always ready to be read. Strobe I/O uses a strobe signal to indicate when valid data is present on data lines to be read. Single handshake I/O involves a peripheral first sending a strobe signal when ready to send data, then the microprocessor acknowledges receipt. Double handshake I/O is like a conversation, with the peripheral and microprocessor each sending strobe and acknowledge signals to indicate readiness to send and receive data.
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- 2. CONTENT RELATED: • SIMPLEI/O • STROBE I/O • SINGLE HANDSHAKE I/O • DOUBLE HANDSHAKE I/O
- 3. SIMPLE I/O • INTHIS METHOD, TO FEED INPUT, A DEVICE IS CONNECTED TO I/O PORT AND READ THE PORT BECAUSE THE DATA IS ALWAYS PRESENT AND READY. • TO OUTPUT A DATA TO A SIMPLE DEVICE AS LED, ALL YOU HAVE TO DO IS CONNECT THE INPUT OF THE LED BUFFER ON AN OUTPUT PORT. THE LED IS ALWAYS THERE AND READY, SO YOU CAN SEND DATA TO IT ANY TIME.
- 4. STROBE I/O • INSOME CONDITIONS, WHENEVER A VALID DATA IS PRESENT ON AN EXTERNAL DEVICE ONLY AT A CERTAIN TIME THEREFORE IT MUST BE READ AT THAT TIME , THIS METHOD IS USED • EXAMPLE; WHEN A KEY IS PRESSED, CIRCUITRY IN THE KEYBOARD SENDS OUT THE ASCII CODES FOR THE PRESSED KEY ON PARALLEL DATA LINES AND SEND OUT THE STROBE SIGNAL ON ANOTHER LINE TO INDICATE VALID DATA IS PRESENT IN THE DATA LINES. • DATA CAN ONLY BE READ WHEN A STROBE PULSE TELLS IF THE DATA IS VALID. (P.S: A STROBE IS A SIGNAL THAT IS SENT THAT VALIDATE THE DATA
- 5. SINGLE HANDSHAKE I/O •IN SINGLE HANDSHAKE, A PERIPHERAL DEVICE FIRST SENDS A "STROBE SIGNAL" TO THE MICROPROCESSOR TO INDICATE THAT IT IS READY TO SEND DATA. • THE MICROPROCESSOR, UPON DETECTING THE STROBE SIGNAL, OPENS UP ITS INPUT PORT AND RECEIVES THE DATA. • AFTER RECEIVING DATA, IT SENDS AN "ACKNOWLEDGE SIGNAL" TO THE PERIPHERAL TO INDICATE THAT TRANSMISSION HAS BEEN COMPLETED. • A TRANSMISSION SESSION HAS BEEN COMPLETED.
- 7. DOUBLE HANDSHAKE I/O •JUST LIKE A CONVERSATION BETWEEN TWO PERSON. • IN DOUBLE HANDSHAKE, FIRST THE PERIPHERAL DEVICE SENDS A STROBE SIGNAL, THEN MICROPROCESSOR SENDS THE ACKNOWLEDGE SIGNAL TO INDICATE THAT IT IS READY TO RECEIVE DATA. • AFTER THAT DATA IS RECEIVED. • AFTER SENDING DATA, THE PERIPHERAL SENDS A STROBE SIGNAL TO INDICATE DATA TRANSMISSION COMPLETION ,DUE TO WHICH, THE MICROPROCESSOR DROPS ITS ACKNOWLEDGE SIGNAL AND A SESSION HAS BEEN COMPLETED.
- 8. Er. Sulav Paudel| MSc