Achronix Speedster22i SerDes - Manual (Page 101)

Example of SerDes Register Access through SBUS: Setting Loopback Mode
The SerDes must be in the “ready” state before it enters loopback mode. Therefore, the
loopback mode cannot be configured with the bitstream, and must instead be configured in
user mode. The ACE library provides the macro ACX_SERDES_LOOPBACK_CTRL to make
that straightforward.
To use this macro, use the following in your code:
`include "speedster22i/macros/ACX_SERDES_LOOPBACK_CTRL.v"
Also, connect an instance of ACX_SERDES_LOOPBACK_CTRL to each SerDes lane, and set
the LOOPBACK_MODE parameter. At startup, the ACX_SERDES_LOOPBACK_CTRL
instance will configure the appropriate loopback mode.
Signals for ACX_SERDES_LOOPBACK_CTRL
As shown in “Figure 45 Connections for ACX_SERDES_LOOPBACK_CTRL”,
ACX_SERDES_LOOPBACK_CTRL has three groups of signals, SerDes signals, control
signals, and pass-through signals.
Figure 45: Connections for ACX_SERDES_LOOPBACK_CTRL
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