FWLXT9785BC.A4 Intel, FWLXT9785BC.A4 Datasheet - Page 119

• Manufacturer Part Number: FWLXT9785BC.A4
• Manufacturer: Intel

Specifications of FWLXT9785BC.A4

• Lead Free Status / RoHS Status: Not Compliant

4.3.2
4.3.3
Datasheet
Document Number: 249241
Revision Number: 010
Revision Date: 30-May-2006
Table 41. MII Mode Select
Figure 8. Internal Loopback
Internal Loopback
Register bit 0.14 must be set to enable internal loopback operation. Register bits 16.14 and 0.8
must be set for 10 Mbps operation. Intel recommends that auto-negotiation be disabled while
internal loopback is enabled. The normal auto-negotiation process code word exchange cannot be
completed.The following two-step sequence is recommended for the most efficient mode change
when enabling forced 100 Mbps internal loopback mode directly from auto-negotiation mode:
This two-step process ensures the 100 Mbps link comes up quickly. If the one-write process of
writing 0x6100h is followed, it may take up to 1.5 seconds before link is established and data is
received on the port. The 1.5 second delay is due to the IEEE auto-negotiation Break Link Timer
(BLT) requirement. The timer must expire before link is established when changing modes directly
from auto-negotiation to internal loopback forced 100 Mbps mode. Use the above two-step process
to eliminate the auto-negotiation BLT timer requirement.
RMII Data Interface
The LXT9785/LXT9785E provides a separate RMII for each network port, each complying with
the RMII Specification, Revision 1.2. The RMII includes both a data interface and an MDIO
management interface. The RMII Data Interface exchanges data between the LXT9785/LXT9785E
and up to eight Media Access Controllers (MACs).
1. Write Register 0 with 0x2100h (forced 100 Mbps), and
2. Write Register 0 with 0x6100h (enable internal loopback with forced 100 Mbps)
1. Invalid for the BGA15 package.
Reserved
SS-SMII
RMII
SMII
1
LXT9785 and LXT9785E Advanced 8-Port 10/100 Mbps PHY Transceivers
ModeSel1
0
0
1
1
RMII/
SMII/
SMII
inter
face
SS-
Digital
Block
ModeSel0
LXT9785/9785E
Loopback
0
1
0
1
Analog
Block
Driver
Driver
Tx
Fx
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