Altera CPRI IP Core - Manual (Page 48)

4–16 Chapter 4: Functional Description
MAP Interface
CPRI MegaCore Function December 2013 Altera Corporation
User Guide
You set the oversampling factor to match the frequency of your active data channels.
The CPRI line rate determines the number of bits in the IQ data block of each basic
frame. If your CPRI IP core has a high line rate and a low oversampling factor, it can
accommodate a larger number of active data channels than if the line rate were lower
or the oversampling factor higher.
In 15-bit mode, inside the CPRI IP core, bits 0 and 16 of the Avalon-ST data are absent
from the compact IQ data word representation. Therefore, despite the fact that in
15-bit mode the IQ data goes out on the data channel in 32-bit words, formatted as
Figure 4–8. Bit Correspondence Between IQ Sample and 32-Bit Avalon-ST Data
16-Bit Width IQ Sample:
Q: I:
15 1 0 15 2 1 0
Avalon-ST Data Word in AxC Container:
31 17 16 15 2 1 0
15-Bit Width IQ Sample:
Q: I:
14 0 14 2 1 0