4.8.3 PLCA Transmit Opportunity Skipping

PLCA transmit opportunity skipping is useful to limit the amount of data low-priority nodes may transmit onto the network. When transmit opportunity skipping is enabled, the PHY is configured to skip a number of PLCA transmit opportunities once a packet has been transmitted. The PHY will yield the skipped transmit opportunities and prevent the MAC from transmitting by asserting the MII CRS or RMII CRSDV pin. Once the specified number of transmit opportunities have been skipped, the PHY will re-enable normal PLCA operation of CRS/CRSDV and permit the MAC to transmit packets when its transmit opportunities occur.

PLCA transmit opportunity skipping is enabled by setting the PLCA Transmit Opportunity Skip Enable (TOSKPEN) bit in the PLCA Skip Control (PLCASKPCTL) register. The number of transmit opportunities to skip after transmitting a packet is configured in the PLCA Transmit Opportunity Skip (PLCATOSKP) register.

Restriction: To prevent undesirable traffic shaping behavior, PLCA transmit opportunity skipping should not be used in conjunction with credit based traffic shaping.