Data Sheet

Ethernet Controller I210 —Interconnects
102
Table 3-25 lists the structure of a 802.3X FC packet.
3.7.5.1.2 Operation and Rules
The I210 operates in Link FC.
• Link FC is enabled by the RFCE bit in the CTRL register.
Note: Link flow control capability is negotiated between link partners via the auto negotiation
process. It is the software device driver responsibility to reconfigure the link flow control
configuration after the capabilities to be used where negotiated as it might modify the value
of these bits based on the resolved capability between the local device and the link partner.
Once the receiver has validated receiving an XOFF, or PAUSE frame, the I210 performs the following:
• Increments the appropriate statistics register(s)
•Sets the Flow_Control State bit in the FCSTS0 register.
• Initializes the pause timer based on the packet's PAUSE timer field (overwriting any current timer’s
value)
• Disables packet transmission or schedules the disabling of transmission after the current packet
completes.
Resumption of transmission might occur under the following conditions:
• Expiration of the PAUSE timer
• Receiving an XON frame (a frame with its PAUSE timer set to 0b)
Both conditions clear the relevant Flow_Control State bit in the relevant FCSTS0 register and
transmission can resume. Hardware records the number of received XON frames.
3.7.5.1.3 Timing Considerations
When operating at 1 Gb/s line speed, the I210 must not begin to transmit a (new) frame more than two
pause-quantum-bit times after receiving a valid link XOFF frame, as measured at the wires. A pause
quantum is 512-bit times.
When operating in full duplex at 10 Mb/s or at 100 Mb/s line speeds, the I210 must not begin to
transmit a (new) frame more than 576-bit times after receiving a valid link XOFF frame, as measured at
the wire.
Table 3-25. 802.3X Packet Format
DA 01_80_C2_00_00_01 (6 bytes)
SA Port MAC address (6 bytes)
Type 0x8808 (2 bytes)
Op-code 0x0001 (2 bytes)
Time XXXX (2 bytes)
Pad 42 bytes
CRC 4 bytes