Visible to Intel only — GUID: nik1409855387894
Ixiasoft
Visible to Intel only — GUID: nik1409855387894
Ixiasoft
4.2.1. Gigabit Ethernet Transceiver Datapath
Functional Mode | Data Rate | High-Speed Serial Clock Frequency | Parallel Recovered Clock and Low-Speed Parallel Clock Frequency | FPGA Fabric-Transceiver Interface Clock Frequency |
---|---|---|---|---|
GbE-1.25 Gbps | 1.25 Gbps | 625 MHz | 125 MHz | 125 MHz |
GbE-3.125 Gbps | 3.125 Gbps | 1562.5 MHz | 312.5 MHz | 156.25 MHz |
8B/10B Encoder
In GbE configuration, the 8B/10B encoder clocks in 8-bit data and 1-bit control identifiers from the transmitter phase compensation FIFO and generates 10-bit encoded data. The 10-bit encoded data is fed to the serializer.
For more information about the 8B/10B encoder functionality, refer to the Transceiver Architecture for Cyclone V Devices chapter.
Rate Match FIFO
In GbE configuration, the rate match FIFO is capable of compensating for up to ±100 ppm (200 ppm total) difference between the upstream transmitter and the local receiver reference clock. The GbE protocol requires that the transmitter send idle ordered sets /I1/ (/K28.5/D5.6/) and /I2/ (/K28.5/D16.2/) during interpacket gaps, adhering to the rules listed in the IEEE 802.3 specification.
The rate match operation begins after the synchronization state machine in the word aligner indicates that the synchronization is acquired-by driving the rx_syncstatus signal high. The rate matcher always deletes or inserts both symbols (/K28.5/ and /D16.2/) of the /I2/ ordered sets, even if only one symbol needs to be deleted to prevent the rate match FIFO from overflowing or underrunning. The rate matcher can insert or delete as many /I2/ ordered sets as necessary to perform the rate match operation.
Two flags are forwarded to the FPGA fabric:
- rx_rmfifodatadeleted—Asserted for two clock cycles for each deleted /I2/ ordered set to indicate the rate match FIFO deletion event
- rx_rmfifodatainserted—Asserted for two clock cycles for each inserted /I2/ ordered set to indicate the rate match FIFO insertion event
For more information about the rate match FIFO, refer to the Transceiver Architecture for Cyclone V Devices chapter.
GbE Protocol-Ordered Sets and Special Code Groups
Code | Ordered Set | Number of Code Groups | Encoding |
---|---|---|---|
/C/ |
Configuration |
— |
Alternating /C1/ and /C2/ |
/C1/ |
Configuration 1 |
4 |
/K28.5/D21.5/ Config_Reg 12 |
/C2/ |
Configuration 2 |
4 |
/K28.5/D2.2/ Config_Reg 12 |
/I/ |
IDLE |
— |
Correcting /I1/, Preserving /I2/ |
/I1/ |
IDLE 1 |
2 |
/K28.5/D5.>6/ |
/I2/ |
IDLE 2 |
2 |
/K28.5/D16.2/ |
- |
Encapsulation |
— |
— |
/R/ |
Carrier_Extend |
1 |
/K23.7/ |
/S/ |
Start_of_Packet |
1 |
/K27.7/ |
/T/ |
End_of_Packet |
1 |
/K29.7/ |
/V/ |
Error_Propagation |
1 |
/K30.7/ |
Synchronization State Machine Parameters | Setting |
---|---|
Number of valid {/K28.5/, /Dx,y/} ordered sets received to achieve synchronization | 3 |
Number of errors received to lose synchronization | 4 |
Number of continuous good code groups received to reduce the error count by 1 | 4 |