AL211 Allayer Communications, AL211 Datasheet - Page 10

• Manufacturer Part Number: AL211
• Description: Fast Ethernet Fiber to TP Media Converter
• Manufacturer: Allayer Communications

Figure 1-5
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D o w n B i t
U p B i t
M S G C L K
The clock rate can be as high as 25 MHz, however the data rate is limited by the IPG between
frame. The worst case data rate is 8 Kbit/s which is based on the calculation of 1518 bytes of data
interleaved with 8-bit of secondary channel data.
The ideal function of a media converter chip is to provide a full duplex transparent media link.
However, because the 100Base-FX does not support auto-negotiation, the AL211 can not propagate
duplex information to the twisted pair media. Although the AL211 does not support full auto-
negotiation, it provides an option to force the link partner into full duplex mode with auto-
negotiated link pulses. When Pin 37, (ENFLP) is pulled high, the AL211 will transmit auto-
negotiation FLP with 100 Mbit/s full duplex capability field forcing the linked unmanaged switch
into full duplex.
The AL211 provides an PECL interface to the TP interface and fiber connect interface. The
intention of the interfaces are to allow design engineers to be able to choose other media
interconnects such as a 1300nm fiber module or external twisted pair equalizer.
The AL211 has the signal detect function built in and does not require any interface to the signal
detect input.
The AL211 provides an on-chip elastic store. With the elastic store in place, the device retimes the
received signal and removes jitter. The elastic store can be turned off to reduce latency of the device
by using the appropriate pins.
For typical applications such as media conversion to a 100Base-FX hub, where the twisted pair
length is less than 10 meters and fiber length is less than 400 meters (reference to IEEE 802.3
clause 29 for fiber length and system configuration), retiming is not needed.
For full duplex application of fiber length over 2km, the elastic store should be used to remove the
jitter from the signal.
2.4 Full Duplex Application
2.5 PECL Interface
2.6 Elastic Store
Secondary Channel Data Format
Start Bit
Reference Only / Allayer Confidential
8 Bit Data
10