Question

write down the concept of frequency justification

Answer 1

When the input data has a rate lower than the output data rate of a multiplexer, the positive stuffing will occur. The input is stored in a buffer at a rate which is controlled by the WRITE clock. Since the output (READ) clock rate is higher than the WRITE clock rate, the buffer content will be depleted or emptied. To avoid this condition, the buffer fill is constantly monitored and compared to a threshold. If the the content fill is below a threshold, the READ clock is inhibited and stuffed bit is inserted to the output stream. Meanwhile, the input data stream is still filling the buffer. The stuffed bit location information must be transmitted to the receiver so that the receiver can remove the stuffed bit.

When the input data has a rate higher than the output data rate of a multiplexer, the negative stuffing will occur. If negative stuffing occur, the extra data can be transmitted through an other channel. The receiver must need to kown how to retrieve the data.