Input Buffer Functionality

In the upstream direction, the repeater also functions as an input buffer to improve network efficiency. Packet timeslots are scheduled for minimum packet spacing, in order to have maximum bandwidth. Yet the phase error between node timers may vary by ±16 MII clocks. Therefore an upstream packet may arrive at a node's OUT port as much as 16 clocks before the node completes sending its own packet. To prevent losing data during this "collision," the OUT port repeater FIFO will be deep enough to hold 16 nibbles of data. After the node finishes sending its own packet, a minimum number of IDLEs are inserted, and finally the upstream packet will be forwarded.