A Block Check Character (BCC) is a form of error-detecting code used in data communication protocols to verify the integrity of blocks of data. It's a method used to detect errors in transmitted data by appending an additional character or characters (usually a checksum or a CRC value) to the end of a block of data. The BCC is calculated based on the contents of the data block, and it changes if any bit in the data block is altered during transmission.
Here's how a Block Check Character typically works:
1. Data Block: The data to be transmitted is divided into fixed-size blocks. This could be a sequence of bytes, characters, or bits, depending on the communication protocol and application requirements.
2. BCC Calculation: A checksum or a CRC value is calculated based on the contents of each data block. This calculation typically involves performing mathematical operations on the binary representation of the data block, resulting in a checksum or CRC value that represents the data block's contents.
3. Appending BCC: The calculated BCC value is appended to the end of the data block before transmission. This creates a larger block that includes both the original data and the BCC.
4. Transmission: The entire block, including the data and the appended BCC, is transmitted over the communication channel to the receiver.
5. Verification: Upon receiving the data block, the receiver recalculates the BCC value based on the received data (excluding the BCC). If the calculated BCC matches the received BCC, it indicates that the data was likely transmitted without errors. If the calculated BCC does not match the received BCC, it suggests that errors may have occurred during transmission, and appropriate error-handling mechanisms can be invoked.
Block Check Characters provide a simple and efficient means of detecting errors in transmitted data, particularly in scenarios where error correction is not required or where more complex error correction techniques are not feasible due to resource constraints. However, it's important to note that BCCs can only detect errors; they cannot correct them. For error correction, more advanced techniques like Forward Error Correction (FEC) or Automatic Repeat reQuest (ARQ) are typically employed.