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lms-chris
Observer
Observer
583 Views
Registered: ‎06-20-2019

100 Mbps Ethernet (100BASE-FX) using GTY

The GTY minimum line-rate of both TX and RX is 500 Mbps. Is it still possible to use the GTY?

For example by,

1. Configure both TX and RX in buffer bypass mode using no encoding (raw) and line-rate 500 Mbps.

2. In TX repeat every bit 4 times. (After 4b/5b encoding in FPGA fabric, the bit rate between GTY and fabric would be 125 Mbps.)

3. In RX, drop 3 out of every 4 bits.

If this works at all, is RX clock recovery possible?

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2 Replies
575 Views
Registered: ‎07-23-2019

 

So you want to fake a lower-than-minimum frequency.

I can't see a problem straight away but if that worked it would exist as a general technique to have any bit rate lower than a minimum.

You are either one step away of fame or failure (let's call the latter 'learning')

The potential problem I see is the RX won't be happy seeing strings of 1's and 0's. In theory it will lock to the harmonic but...

Interesting thing. Good luck!

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lms-chris
Observer
Observer
526 Views
Registered: ‎06-20-2019

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