FLLXT1000BA.C4QE000 Intel, FLLXT1000BA.C4QE000 Datasheet - Page 44

• Manufacturer Part Number: FLLXT1000BA.C4QE000
• Manufacturer: Intel

Specifications of FLLXT1000BA.C4QE000

• Lead Free Status / RoHS Status: Not Compliant

LXT1000 — Gigabit Ethernet Transceiver
2.4.9.2
2.4.9.3
44
2.4.9.1.1 Using SmartSpeed
Smartspeed is enabled by pulling SMART_SPD High or by setting 16.7 = 1. When SmartSpeed
downgrades the LXT1000 advertised capabilities, it sets bit 18.9. When link is established, its
speed is indicated in 17.15:14. SmartSpeed automatically resets the highest-level auto-negotiation
abilities advertised, if link is established and then lost for more than 2 seconds.
Auto-Negotiate Isolation
Auto-Negotiate Isolation functions whenever the link drops unexpectedly and is re-established at a
different speed. Auto-Negotiate Isolation is enabled when the ANISOL input is set High. Then,
when a link speed change occurs, the LXT1000 sets bit 16.2 and holds all data transfers to or from
the MAC until 16.2 is cleared. The LXT1000 indicates the changes in link state through its
Interrupt function (Register 18), which operates independently of Auto-Negotiate Isolation.
When activated, the auto-negotiate isolation function is asynchronous to the MAC Interface. It may
cause the abrupt termination of a packet as well as setup and hold violations on the receive signals
output by the MAC Interface.
Flow Control
Flow control is a function which is described in Clause 31 of the IEEE 802.3 standard. It allows
congested nodes to pause traffic. Flow control is essentially a MAC-to-MAC function. MACs
indicate their ability to implement flow control during auto-negotiation. This ability is
communicated through two bits in the auto-negotiation registers (4.10 and 4.11).
The LXT1000 transparently supports MAC-to-MAC advertisement of flow control through its
auto-negotiation process. Prior to auto-negotiation, the MAC indicates its flow control capabilities
via 4.10 (Pause) and 4.11 (ASM_DIR). After auto-negotiation, the link partner’s flow control
capabilities are indicated in 5.10 and 5.11.
There are two forms of flow control that can be established via auto-negotiation: symmetric and
asymmetric. Symmetric flow control is for point-to-point links; asymmetric for hub-to-end-node
connections. Symmetric flow control allows either node to flow-control the other. Asymmetric
flow control allows a repeater or switch to flow-control a DTE, but not vice versa.
Table 23
information is provided for reference only, it is the responsibility of the MAC to implement the
correct function. The LXT1000 merely allows the two MACs to communicate their abilities to
each other.
shows intended operation for the various settings of ASM_DIR and Pause. This
Document #: 249276
Rev. Date: 07/20/01
Revision #: 002
Datasheet