An Ethernet port received packet can be sent cut-thru to all destination ports when the following is true:
- The CPSW_CONTROL_REG[19] CUT_THRU_ENABLE bit is set, and
- The receive port is full duplex, and
- The Ethernet receive port speed is non-zero, and
- The packet was received on an express priority, and
- The Ethernet receive port has the remapped received packet priority enabled via the CPSW_PN_CUT_THRU_REG_k[15-8] RX_PRI_CUT_THRU_EN field, and
- All Ethernet destination ports have the remapped packet priority enabled via the CPSW_PN_CUT_THRU_REG_k[7-0] TX_PRI_CUT_THRU_EN field, and
- All Ethernet destination ports are full duplex, and
- All Ethernet destination ports are express priorities, and
- All Ethernet destination ports have a non-zero CPSW_PN_SPEED_REG_k[3-0] SPEED, and
- All Ethernet destination ports are equal to or slower in speed than the Ethernet receive port, and
- The host port is not in the destination port list unless the CPSW_P0_CONTROL_REG[19] CUT_MODE_ETH bit is set.
Whether or not a packet actually egresses cut-thru (with or without delay) on an Ethernet destination port depends on traffic congestion on that port. Cut-thru is compatible with Intersperced Express Traffic (IET) and Enhanced Scheduled Traffic (EST).