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 Enhanced Scheduled Traffic
(EST).