Altera CPRI IP Core - Manual (Page 188)

E–10 Appendix E: Delay Measurement and Calibration
Single-Hop Delay Measurement
CPRI MegaCore Function December 2013 Altera Corporation
User Guide
6. Calculate the full Rx path delay to the AUX interface by adding the values you
derived in step 1 through step 5 . For the example, calculate the Rx path delay as
follows:
Rx path delay = T_txv_RX + <delay through Rx Receive buffer>
+ < rx_byte_delay value> + < cal_pointer value>
+ <delay to AUX IF>
= 5.7 + 33.236 + 0 + 3 + 5 cpri_clkout clock cycles
= 46.936 cpri_clkout clock cycles
Arria V GT 9.8 Gbps
Arria V GT 9.8 Gbps variations use a soft PCS, and are a special case. The following
sections describe the unique differences of these variations.
Rx Path Delay Components
Figure E–4 shows the Rx path delay components in a CPRI IP core variation that
targets an Arria V GT device and was originally configured with the CPRI line rate of
9.8 Gbps. This figure illustrates the Rx path delay components in Arria V GT
variations whose CPRI line rate was auto-negotiated down from the configured CPRI
line rate of 9.8 Gbps to a lower line rate, as well.
The figure shows the relation between the two Rx paths, the path through the AUX
module and the path through the MAP interface module but not through the AxC
interface blocks.
In the CPRI IP core variations that target an Arria V GT device, and were configured
with a with a CPRI line rate of 9.8 Gbps, the link delay (1.) includes the following
delays:
a. Fixed delay through the PMA configured with the Altera Native PHY IP core.
b. Delay through an Rx buffer between the PMA and the PCS. The “Extended Rx
Delay Measurement” section shows how to calculate this delay.
c. Fixed delay through the PCS.
d. Variable delay introduced by round-trip delay calibration feature. Refer to
“Round-Trip Calibration Delay” on page E–7 and “Dynamic Pipelining for
Automatic Round-Trip Delay Calibration” on page E–19 . This delay
component is common to all CPRI IP core variations.
The following sections describe the individual delays and how to calculate them.
Figure E–4. Rx Path Delay in Arria V GT Variations Configured with a CPRI Line Rate of 9.8 Gbps
AxC IF 0
AxC IF n
...
AUX Interface
Data Channels
PMA
Receiver
rx_datain
Physical Layer
CPRI MAP
Interface Module
AUX
Module
Rx Buffer
(1a)
PCS
(1c) (1b)
(2)
(2)
(1d)