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The table below lists the specifications for this design:
Attribute | Specification |
---|---|
Device Family | Cyclone IV GX |
FPGA | Not Specific |
Quartus Version | 13.0 |
Modelsim Version | Modelsim SE v6.6d |
Data rate | 1.25Gbps |
Data Pattern | From Spirent Tester or User self generated |
Number of Channel | 1 |
IP used | ALTGX Basic, Transceiver Reconfiguration Controller |
In transceiver Basic mode, Rate match FIFO is used to compensate the clock frequency difference between local CDR recovered clock and upstream transmitter clock by insert and delete the special rate match characters.Rate match FIFO can compensate for small clock frequency up to +/- 300PPM.
Mostly of the users thought that the hard rate match FIFO's deletion/insertion method for Transceiver Basic mode is same as Transceiver GIGE mode. However, this is totally wrong because in Basic mode, the deletion/insertion was based on /K-S/ ordered set. A /K-S/ ordered set is defined as a /K/ followed by a consecutive number of /S/ (KSSS).The symbols inserted/deleted are /S/ only.Besides that, when rate match FIFO's full signal was asserted, the rate match FIFO will automatic delete the data byte that cause the FIFO to go full. For further info on how transceiver rate match FIFO perform deletion/insertion in Basic mode, please refer to Altera Device Handbook Vol.2, Transceiver Functional Modes chapter.
Below diagram show how the deletion,insertion,FIFO full condition happen in Basic mode.
This problem can be replicated via controlling the clock difference between TX and RX side as shown in diagram below.
Both dev kit's reference clock is synchronized.This will ease for control the PPM difference between local CDR recovered clock and upstream transmitter clock. The pattern sequence been used is …IPG->DATA->IPG->DATA…, Where IPG= BC50, DATA=55AA. By just increased 10PPM at TX side, we can observe the result via SignalTap. Capture the signal at the RX through SignalTap.
Soft Rate Match FIFO Design
User need to design a soft RM FIFO that will able to perform full |C2| (BC420000) character deletion during AN process and deletion/insertion of |I2| character during inter-packet gap.
High-level description:
There is a need of data-width conversion from 16-bit to 8-bit because soft RM FIFO is 8- bit data width while RX transceiver is 16-bit dataout.
Soft Rate Match FIFO Architecture
Rate Match FIFO Depth Calculation
Data packet size – (data packet size x (1 Million +/- PPM )/1 Million) = offset
For example
2 counter using different clock source
PPM = +/- 400 PPM
Data packet size = 10K byte (etc: Jumbo frame)
Calculation:
10K – (10K x (1Million +/- 400)/1 Million) = +/- 4
Soft Rate Match FIFO File (ZIP)
Cyclone IV, ALTGX Basic, Rate Match FIFO, IEEE 802.3 Clause 37 1000BASE-X Auto-Negotiation, SGMII Auto-Negotiation
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