Other Parts Discussed in Thread: AFE7900, AFE7950
Tool/software:
Can you confirm the following?
SerDes rate ranges for AFE79xx (considered P/N - AFE7900)
The AFE7900 data sheet (clause 7.3.7) states that Serdes has the following rates:
- Full rate 18.5 - 29.5 Gbps
- Half rate 9.25 - 16.25 Gbps
- Quarter rate 4.625 to 8.12 Gbps
- 1/8th rate 2.375 to 4.062 Gbps
- 1/16th rate 1.1875 to 2.031 Gbps
1/8th Rate and 1/16th Rate confuses us because:
1) In the AFE7900 Digital Electrical Characteristics data sheet (clause 6.8), we see that the SerDes bit rate has only 3 ranges:
- Full Rate 19 to 29.5 Gbps
- Half Rate 9.5 to 16.25 Gbps
- Quarter Rate 4.75 to 8.125 Gbps
2) Figure 7-106 shows that each SerDes block (4Tx/4Rx) has its own common PLLs for the 4Tx and 4Rx lanes, and the PLL divider for each lane can only be 1, 2 or 4; the VCO PLL range (clause 7.3.7.4) is 19.5 GHz to 32.5 GHz, so it is clear how quarter rate can be achieved, but there is no information about 1/8 rate and 1/16 rate.
3) In the AFE79xx Configuration Guide (clause 3.1. p.20): “there are per lane dividers of 1/2/4/8 between each group of STX/SRX”, this means that the PLL also has divider by 8, if so, then 1/8th rate can be achieved we guess, but still no information about 1/16th rate
4) We tried doing a configuration in Latte iGui to see if the configured rate is suitable or not, and it seems that rates down to 1.1875 Gbps are indeed supported.
So our questions are as follows:
1) What exactly are the SerDes rates (bit rates between JESD devices) that the AFE7900 supports?
2) Is this true for the entire AFE79xx family, or does it vary from P/N to P/N? (rates supported by the AFE7900 are different from rates supported by the AFE7950, for instance)
