IP-CPRI Altera, IP-CPRI Datasheet - Page 72

• 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

4–48
CPRI MegaCore Function User Guide
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However, the CPRI MegaCore function does not provide the values of T12 and T34.
Instead, use the following formula to calculate the round-trip cable delay T14 in
cpri_clkout cycles:
T14 = rx_round_trip_delay – <REC Rx path delay> – <REC Tx path delay>
Use the following formula to calculate the Toffset delay:
The formula to calculate the round-trip cable delay in a single-hop system is
Round-Trip Calculations for a Multi-Hop Configuration
In a multi-hop system, we must combine the delays between and through the
different CPRI RE masters and CPRI RE slaves to determine the round-trip delay.
The value in the rx_round_trip_delay field of the CPRI_ROUND_DELAY register is
meaningful only in CPRI REC and RE masters. It records the round-trip delay for the
current hop only, as shown in
To determine the round-trip delay of a full multi-hop system, you must add together
the values in the CPRI_ROUND_DELAY registers of the REC and RE masters in the system,
plus the delays through the external routers. Use the following calculation, based on
the labels in
Round-trip delay = rx_round_trip_delay (hop i) +  (TBdelayUL + TBdelayDL)(j)
where the REC and RE masters in the configuration are labeled i=0,1,...,n and the
routing layers in the configuration, and their uplink and downlink delays, are labeled
j=0,1,...,(n-1).
To determine the local round-trip cable delay at each hop, use the method described
in
REC or RE master and the RE slave at the current hop. Half of the resulting value is
assumed to be the cable delay in each direction at the current hop.
“Round-Trip and Cable Delay Calculations for a Single-Hop
The sum of the Rx and Tx path delays in the CPRI RE
T34—The delay from CPRI RE to CPRI REC
where
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Toffset = <RE Rx path delay> + <RE Tx path delay>, for the path delay values in the
RE slave
Round-trip cable delay = T14 – Toffset
rx_round_trip_delay is the value in the CPRI_ROUND_DELAY register at offset
0x38
<REC Rx path delay> is the Rx path delay, described in
page
<Tx path delay> is the Tx path delay, described in
page
(Table 6–18 on page
4–40, for the values in the CPRI REC master
4–46, for the values in the CPRI REC master
Figure 4–20 on page
Figure 4–19 on page
6–9)
4–40:
4–40.
“Tx Path Delay” on
December 2010 Altera Corporation
Chapter 4: Functional Description
“Rx Path Delay” on
Configuration”, for the
Delay Measurement