Altera CPRI IP Core - Manual (Page 189)

Appendix E: Delay Measurement and Calibration E–11
Single-Hop Delay Measurement
December 2013 Altera Corporation CPRI MegaCore Function
User Guide
Rx Transceiver Latency
In Arria V GT variations configured with a CPRI line rate of 9.8 Gbps, the Rx
transceiver latency includes fixed delays through the PMA and soft PCS, and a
variable delay through a buffer. The
“Extended Rx Delay Measurement” section
shows how to calculate the variable delay through the Rx buffer between the
PMA and the PCS.
In the Arria V GT variations originally configured with a CPRI line rate of
9.8 Gbps, the fixed latency is the sum of the delays through the PMA and the soft
PCS. These values correspond to
T_txv_RX in Figure E–1 .
Table E–4 describes the fixed latency for Arria V GT devices configured with a
CPRI line rate of 9.8 Gbps.
Extended Rx Delay Measurement
The extended delay measurement is calculated as described in “Extended Rx
Delay Measurement” on page E–6 for other device variations.
CPRI IP core variations that target an Arria V GT device and were originally
configured with a CPRI line rate of 9.8 Gbps do not have an Rx elastic buffer
outside the transceiver. In these variations, the same calculation applies to the Rx
buffer inside the transceiver, instead.
Note this case includes Arria V GT variations originally configured with CPRI
line rate 9.8 Gbps that are running at a lower CPR line rate after autorate
negotiation.
Fixed-Core Delay
In the Rx path, the delay from the Rx transceiver to the Rx elastic buffer, and the
delay from the CPRI low-level receiver block to the AUX interface or through the
MAP interface block, are fixed. This combined delay depends on the device
family and CPRI data rate. This delay is the fixed delay component of the delay
labeled T_R1 in
Figure E–1 on page E–2 .
Table E–4. Fixed Latency T_txv_RX Through Rx Transceiver in Arria V GT 9.8 Gbps CPRI IP Core
CPRI Line Rate
(Gbps)
Latency Through Transceiver in cpri_clkout Clock Cycles
CPRI IP Core Variations
with Hard PCS
Arria V GT (1) Device
Soft PCS Variations on
Arria V GT Device (3)
9.8304 — (2) , Refer to Table E–1 on page E–5
Notes to Table E–4 :
(1) If you configure your CPRI IP core with the CPRI line rate of 9.8304 Gbps, and target an Arria V GT device, the IP
core is configured with a soft PCS. The soft PCS configuration does not change with autorate negotiation to a lower
frequency. This column describes variations that are not configured with a soft PCS.
(2) Arria V GX devices do not support a CPRI IP core line rate of 9.8304 Gbps. Arria V GT devices support a CPRI IP
core line rate of 9.8304 Gbps only in soft PCS variations.
(3) The values described in this column apply to all Arria V GT variations that are configured with a CPRI line rate of
9.8304 Gbps, even after autorate negotiation to a lower frequency. These variations cannot auto-negotiate to a
CPRI line rate of 0.6144 Gbps.