IP-CPRI Altera, IP-CPRI Datasheet - Page 43

• Manufacturer Part Number: IP-CPRI
• Description: IP CORE - Common Public Radio Interface (CPRI)
• Manufacturer: Altera

Specifications of IP-CPRI

• Software Application: IP CORE, Interface And Protocols, HIGH SPEED
• Supported Families: Arria II GX, Cyclone IV GX, HardCopy IV, Stratix IV
• Core Architecture: FPGA
• Core Sub-architecture: Arria, Cyclone, Stratix
• Rohs Compliant: NA
• Lead Free Status / RoHS Status: na
• Lead Free Status / RoHS Status: na

Chapter 4: Functional Description
Physical Layer
December 2010 Altera Corporation
You must realign and resynchronize the Rx elastic buffer after a dynamic CPRI line
rate change. Because resynchronizing the Rx elastic buffer resets its pointers, you
must ensure that the Rx elastic buffer is empty before it is resynchronized. Program
the CPRI_RX_DELAY_CTRL register to realign and resynchronize the Rx elastic buffer.
The Rx elastic buffer adds variable delay to the Rx path through the CPRI MegaCore
function. Refer to
Descrambling
If the tx_prot_version field of the CPRI_TX_PROT_VER register
page
the low-level CPRI receiver may need to descramble the incoming data, depending on
the values in the CPRI_RX_SCR_SEED register. When the rx_scr_act_indication field
of the CPRI_RX_SCR_SEED register
receiver descrambles the data words according to the CPRI V4.1 Specification, using
the seed in the rx_scr_seed field of the CPRI_RX_SCR_SEED register. The seed value
may be zero, indicating the incoming data is not scrambled.
Performing Frame Synchronization
During frame synchronization, LOF is set to zero. LOS—the assertion of the gxb_los
signal—resets the frame synchronization state machine. Auto-rate negotiation occurs
in the first stage of frame synchronization, XACQ1.
synchronization state machine. If scrambling is configured in the CPRI link partner
(based on the value at Z.2.0 in the incoming CPRI communication), additional actions
and conditions apply on the state machine transitions, according to the CPRI V4.1
Specification. The CPRI MegaCore function sets the values in the CPRI_RX_SCR_SEED
register according to these conditions.
6–11) holds the value 2, and the CPRI data rate is 4195.2 Mbps or 6144.0 Mbps,
“Extended Rx Delay Measurement” on page
(Table 6–27 on page
Figure 4–10
6–12) is set, the low-level CPRI
CPRI MegaCore Function User Guide
(Table 6–25 on
4–42.
shows the frame
4–19