User guide

16–16 Chapter 16: Transceiver Reconfiguration Controller IP Core
DFE Registers
Altera Transceiver PHY IP Core November 2012 Altera Corporation
User Guide
Refer to Changing Transceiver Settings Using Register-Based Reconfiguration for the
procedures you can use to control the Eye Monitor.
DFE Registers
The DFE is an infinite impulse response filter (non-linear) that compensates for
inter-symbol interference (ISI). Because the values of symbols previously detected are
known, the DFE engine can estimate the ISI contributed by these symbols and cancel
out this ISI by subtracting the predicted value from subsequent symbols. This
mechanism allows DFE to boost the signal to noise ratio of the received data. You can
use DFE in conjunction with the receiver's linear equalization and with the
transmitter's pre-emphasis feature. DFE is only available for Stratix V devices.
DFE automatically runs offset calibration and phase interpolator (PI) phase
calibration on all channels after power up. You can run DFE manually to determine
the optimal settings by monitoring the BER of the received data at each setting and
specify the DFE settings that yield the widest eye.
0x2 [5:0] RW Vertical height
Taken together, the horizontal phase and
vertical height specify the Cartesian x-y
coordinates of the point on the eye diagram that
you want to sample. You can specify 64 heights
on the vertical axis.
0x3
[15:14] RMW
Reserved
You should not modify these bits. To update this
register, first read the value of this register then
change only the value for bits that are not
reserved.
[13] RW
1D-Eye
Writing a 1 to this bit selects 1D Eye mode and
disables vertical height measurement. Writing a 0
to this bit selects normal 2D Eye measurement
mode including both the horizontal and vertical
axes. You must use 1D Eye mode if you have
enabled DFE.
[12:11] RMW
Reserved
You should not modify these bits. To update this
register, first read the value of this register then
change only the value for bits that are not
reserved.
[10:9] RW
Bandwidth
Sets the EyeQ bandwidth based on receiver
channel data rate. The following encodings are
defined:
■ 2’b00: data rate < 1 Gbps
■ 2’b01: data rate > 1 Gbps and <= 2.5 Gbps
■ 2’b10: data rate > 2.5 Gbps and <= 7.5 Gbps
■ 2’b11: data rate > 7.5 Gbps
[8:0] RMW
Reserved
You should not modify these bits.To update this
register, first read the value of this register then
change only the value for bits that are not
reserved.
Table 16–13. EyeQ Offsets and Values (Part 2 of 2)
Offset Bits R/W Register Name Description