AL211 Allayer Communications, AL211 Datasheet - Page 9

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

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The AL211’s 100Base-TX receiver is designed for data reception of up to a maximum of 10 meters
of Category 5 Cable. For applications that require the full IEEE 802.3 distance (100 meters), the
AL211 provides PECL interface to interface to an external equalizer chip. However, media
converter applications are typically within the wiring closet. A distance of 10 meters is adequate to
support these applications.
After the scrambled MLT3 signal from the twisted pair port is received by the AL211, the device
descrambles the signal and converts it into a NRZ signal stream. The signal is then passed through
an elastic store for retiming. The resulting signal is then converted into a serial NRZI bit stream and
sent to the LED driver. The elastic store can be disabled to reduce the latency of the converter.
During idle, the AL211 will transmit an IDLE signal. If the twisted pair port is in a link-down state,
the AL211 will cease to transmit any signal and link fault is thus propagated.
The AL211 100Base-FX receiver is comprised of a scrambler and a quantizer. After receiving the
serial bit stream from the PIN amplifier, the device passes the signal through an elastic store for
retiming and converts the NRZI coded data into a scrambled MLT3 signal and sends it to the
100Base-TX transmitter.
During idle, the AL211 will transmit the scrambled IDLE signal. If the fiber receiver does not
receive any idle signal, the fiber port will go into a link-down state and the AL211 will perform two
tasks:
In the event of remote fault (the receiver receives the far-end fault signal), the receiver will go into a
link-down state. The RF LED provides the remote fault signal status indication. The far-end fault
signal is indicated by the far-end fault IDLE signal (84 “ones” follow by a “zero”).
When the fiber port is in a link-down state (either remote fault or receive link-fail), the device will
put the TP output port into high impedance and assert Redun# signal.
The AL211 provides a secondary serial communication channel. This serial port is intended as a
point to point communication link piggybacked to the 100 Mbit/s data stream over the fiber. The
data is input and retrieved from the AL211’s media conversion device serial port.
The secondary channel data is transmitted during the IPG of the normal transmission stream.
During idle (or IPG), the AL211 will insert a 10-bit code word and an 8-bit data into the transmit
data stream. When a regular data transmission is in progress, the secondary channel will remain
idle. The data written into the AL211 will be stored in the on-chip FIFO.
If additional data is written into the AL211 before the stored data has been sent, it will write over
the previous data.
2.1 100Base-TX to 100Base-FX Conversion
2.2 100Base-FX to 100Base-TX Conversion
2.3 Secondary Channel
1. Cease to transmit any signal to the TP port and put the transmit TP port in high
2. Simultaneously start transmitting far-end fault signals.
impedance; and
Figure 1-5
Reference Only / Allayer Confidential
illustrates the secondary channel data format.
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