Handling Status Signals

Manages signals that indicate the status of peripheral devices.

Duplexity

Duplexity refers to the direction and method of data transmission between two devices.

• Simplex: Data can only be transmitted in one direction. One device is always the sender, and the other is always the receiver.
• Half-Duplex: Data can be transmitted in both directions, but only one direction at a time. Communication alternates between sending and receiving.
• Full-Duplex: Data can be transmitted in both directions simultaneously, allowing faster and more efficient communication.

Connections

Connection have 3 types:

• Asynchronous Connections: Transfer data in smaller frames
• Synchronous Connections: Transfer data in large frames
• Isochronous Connections: Used to handle real time application

Synchronous vs Asynchronous Example

Asynchronous connection (700K chars file):

• Each character has a start bit, stop bit, and possibly a parity bit.
• Data size: 700,000 chars × 11 bits (8 bits data + 1 start + 1 stop + 1 parity) = 7,700,000 bits.

Synchronous connection (700K chars file):

• Assumes a maximum payload size of 1500 bytes (1,500 characters per frame).
• Each frame contains 5 bytes of overhead (1-byte header, 1-byte address, 1-byte control, 2-byte checksum).
• Data size:
  • 1500 bytes payload + 5 bytes overhead = 1505 bytes per frame.
  • 467 frames × 1505 bytes = 716,380 bytes, or 5,731,040 bits.

Conclusion: Synchronous connections require significantly less data for the same file transfer compared to asynchronous connections due to the reduced overhead.