* Question
What is the structure of a short frame, and what fields does it contain?
* Answer
In digital communication systems, a frame is a structured block of bits used to encapsulate data for transmission over a network or channel.
A short frame refers to a compact frame format that carries a limited amount of user data along with essential control information.
It is widely used in protocols where low latency, fast synchronization, and minimal overhead are critical — such as industrial control networks, sensor communication, and low-power wireless systems.
1. Frame Delimiters
A short frame typically begins and ends with frame delimiters, which mark the start and end of the frame.
Start Delimiter (SD): Signals the receiver to begin reading the incoming bits as a new frame.
End Delimiter (ED): Indicates that the frame is complete.
These delimiters ensure synchronization between the transmitter and receiver.
2. Address Field
The address field identifies the source and/or destination of the data within the network.
In short-frame systems, this field is usually shortened (for example, 1 or 2 bytes) to reduce overhead while still supporting basic point-to-point or small network addressing.
3. Control Field
The control field carries essential frame type, sequence number, and acknowledgment information.
It defines the function of the frame — such as data transmission, acknowledgment (ACK), or command signaling.
In many short-frame protocols, this field also helps manage error control and flow regulation without complex headers.
4. Information Field (Payload)
This is the data-carrying section of the frame.
In a short frame, the payload is typically very small—sometimes just a few bytes—since the focus is on fast control signaling rather than bulk data transfer.
For example, sensor readings or control instructions are often transmitted in this compact format to minimize latency.
5. Frame Check Sequence (FCS)
At the end of the frame, a Frame Check Sequence (commonly a CRC or checksum) is used to verify data integrity.
When the receiver detects a mismatch between the transmitted and calculated FCS values, it can discard or request retransmission of the frame.
This ensures reliable communication even in noisy or high-interference environments.
Summary
A typical short frame structure includes:
Start Delimiter → Address Field → Control Field → Information Field → Frame Check Sequence → End Delimiter
This compact design allows fast, efficient, and reliable data exchange in systems where bandwidth or power is limited.
Short frames are especially useful in industrial fieldbuses, sensor networks, and real-time embedded communications, where responsiveness and synchronization matter more than payload size.
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