| 摘要 |
The SPE of an incoming STS-3 type signal is demultiplexed into three STS-1 payloads and fed to three FIFOs (45-1, 45-2, 45-3), and a byte which is synchronous with the TOH is tracked through the three FIFOs (45-1, 45-2, 45-3) to provide an indication of the FIFO depth. A frame count is also kept to track the number of frames since a last pointer movement. Stuffs or destuffs are generated based on the FIFO depth as well as based on the frame count, with a stuff or destuff generated as quickly as four frames from a previous pointer movement if the FIFO is close to full or close to empty, and less quickly (e.g., at thirty-two frames from a previous pointer movement) if the FIFO is only starting to empty or to fill. Where the STS-3 type signal is an STS-3C signal, the decision on whether to stuff or destuff is made with reference to all three depth measurement circuits (48-1, 48-2, 48-3) as all the STS-1 payloads must be stuffed or destuffed together. |
