Altera CPRI v6.0 MegaCore Function - Manual (Page 80)

Table 3-29: Loopback Modes
Tag in Figure Description How to Configure
1 External loopback: Use this configuration
to test the full Tx and Rx paths from an
application through the CPRI link and
back to the application.
Connect a CPRI REC master's CPRI Tx interface
to its CPRI Rx interface by physically connecting
the CPRI v6.0 IP core's high-speed transceiver
output pins to its high-speed transceiver input
pins.
The connection medium must support the data
rate requirements of the CPRI v6.0 IP core.
2 Transceiver PMA serial forward loopback
path is active.
Turn on Enable transceiver PMA forward
loopback path (Tx to Rx) in the parameter editor
and set the
loop_forward
field of the
LOOPBACK
register to the value 2'b01.
3 Active parallel loopback path does not
exercise the transceiver.
Turn on Enable forward loopback path (Tx to
Rx) in the parameter editor and set the
loop_
forward
field of the
LOOPBACK
register to the value
2'b10 (to include the stitching logic to the
transceiver) or 2'b11 (to exclude the stitching
logic to the transceiver).
4 Reverse loopback path is active. Turn on Enable reversed loopback path (Rx to
Tx) in the parameter editor and set the
loop_
reversed
field of the
LOOPBACK
register to a non-
zero value. The register value specifies the parts of
the CPRI frame that participate in the loopback
path. Other parts of the CPRI frame are filled in
from the local IP core.
Related Information
LOOPBACK Register on page 5-14
CPRI v6.0 IP Core Self-Synchronization Feature
Altera provides a self-synchronization testing feature that supports an RE slave in a CPRI link external
loopback configuration. This feature is intended to work correctly only for Layer 1 testing.
By default, only an REC master can function correctly in a CPRI link external loopback configuration. An
RE slave in external loopback configuration cannot achieve frame synchronization, because the CPRI RX
interface must lock on to the K28.5 character before the CPRI TX interface can begin sending K28.5
characters. Therefore, no K28.5 character is ever transmitted on the RE slave loopback CPRI link.
However, in an Altera RE slave CPRI v6.0 IP core you can specify that the CPRI TX interface begin
sending K28.5 characters before the CPRI Rx interface locks on to the K28.5 character from the CPRI link.
This feature supports a CPRI RE slave in achieving frame synchronization without being connected to a
CPRI master, and allows you to test your CPRI RE slave without the need for an additional CPRI v6.0 IP
core.
To turn on this feature, connect your CPRI RE slave in a CPRI link external loopback configuration, and
set the
tx_enable_force
field of the
L1_CONFIG
register to the value of 1.
3-50 CPRI v6.0 IP Core Self-Synchronization Feature
UG-01156
2014.08.18
Altera Corporation Functional Description
Send Feedback