Altera Corporation
2–203
October 2007
Stratix II GX Device Handbook, Volume 2
Stratix II GX Transceiver Architecture Overview
Table 2–48
shows the uncertainty in the CPRI transceiver data path after
delay adjustment.
Table 2–48
shows that the CPRI link delay accuracy requirements are met
within the transceiver data path.
Transceiver Limitations in CPRI Mode
To meet the CPRI link delay accuracy requirements, the Quartus II
software adjusts delays on the clock routes from the
tx_clkout
and
rx_clkout
ports to the write and read ports of the transmitter and
receiver phase compensation FIFOs, respectively, for each transceiver
channel. Due to this requirement, the Quartus II software only allows the
tx_clkout
signal from each channel to clock the write port of its
transmitter phase compensation FIFO. Similarly, it allows the
rx_clkout
signal from each channel to clock the read port of its receiver
phase compensation FIFO. If your design requires dynamic
reconfiguration between CPRI mode and other modes, each channel’s
phase compensation FIFOs must be clocked by its own
tx_clkout
and
rx_clkout
for other modes as well. The default transceiver
configuration used to create the programming file (
.sof
or
.pof
) must be
CPRI for the delay algorithm to take effect.
In CPRI mode, you cannot group the
tx_coreclk
and/or
rx_coreclk
ports of multiple channels and drive them using a common clock driver
using the shared clock or 0 PPM clock group assignments. Each CPRI
channel will utilize at least two global and/or regional clock resources.
Since a maximum of 32 global and/or regional clock resources are
available for transceivers in the Stratix II GX device, the clock resource
availability governs the maximum number of CPRI channels that you can
instantiate per device.
Table 2–48. Uncertainty in CPRI Transceiver Datapath Latency With Delay Adjustment
Note (1)
Data Rate
(Mbps)
Receiver
Deserializer
Uncertainty
(Parallel Clock
Cycles)
Receiver Phase
Comp FIFO
Uncertainty
(Parallel Clock
Cycles)
Transmitter
Phase Comp FIFO
Uncertainty
(Parallel Clock
Cycles)
Parallel Clock
Period (ns)
Total
Uncertainty
(ns)
614
0.9
0
0
16.3
14.67
1228
0.9
0
0
8.15
7.34
Note to
Table 2–48
:
(1)
The delay adjustment is not made for CPRI 2456 Mbps line rate configuration since it meets the 16.3 ns link delay
requirement without these adjustments.