Loopback Modes
The Stratix GX transceiver has built-in loopback modes to aid in debug
and testing. The loopback modes are set in the Stratix GX MegaWizard
Plug-In Manager in the Quartus II software. Only one loopback mode can
be set at any single instance of the transceiver block. The loopback mode
applies to all used channels in a transceiver block.
The available loopback modes are:
■
■
■
Serial loopback
Parallel loopback
Reverse serial loopback
Serial Loopback
Serial loopback exercises all the transceiver logic except for the output
buffer and input buffer. The loopback function is dynamically switchable
through the rx_slpbkport on a channel by channel basis. The VOD of the
output reduced. If you select 400 mV, the output is tri-stated when the
serial loopback option is selected. Figure 2–21 shows the data path in
serial loopback mode.
Figure 2–21. Data Path in Serial Loopback Mode
BIST PRBS
Verifier
BIST
Incremental
Verifier
Word
Aligner
Deserializer
Channel
Aligner
Rate
Matcher
8B/10B
Decoder
Phase
Compensation
FIFO
Byte
Deserializer
Clock
Recovery
Unit
Byte
Serializer
Phase
Compensation
FIFO
Serializer
8B/10B
Encoder
BIST
Generator
Active Path
BIST PRBS
Generator
Non-Active Path
2–26
Stratix GX Device Handbook, Volume 1
Altera Corporation
June 2006
ALTERA [ ALTERA CORPORATION ]
