DS280DF810ABVT datasheet(27/51 Pages) TI1

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4032

4095

Phase Position

DS280DF810

www.ti.com

SNLS538A – SEPTEMBER 2016 – REVISED OCTOBER 2019

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A full eye diagram capture can be performed when the CDR is locked. The eye diagram is constructed within a

64 x 64 array, where each cell in the matrix consists of an 16-bit word representing the total number of hits

recorded at that particular phase and voltage offset. Users can manually adjust the vertical scaling of the EOM or

allow the state machine to control the scaling which is the default option. The horizontal scaling controlled by the

state machine and is always directly proportional to the data rate.

When a full eye diagram plot is captured, the retimer will shift out four 16-bit words of junk data that should be

discarded followed by 4096 16-bit words that make up the 64 × 64 eye plot. The first actual word of the eye plot

from the retimer is for (X, Y) position (0,0), which is the earliest position in time and the most negative position in

voltage. Each time the eye plot data is read out the voltage position is incremented. Once the voltage position

has incremented to position 63 (the most positive voltage), the next read will cause the voltage position to reset

to 0 (the most negative voltage) and the phase position to increment. This process will continue until the entire

64 × 64 matrix is read out. Figure 14 below shows the EOM read out sequence overlaid on top of a simple eye

opening plot. In this plot any hits are shown in green. This type of plot is helpful for quickly visualizing the HEO

and VEO. Users can apply different algorithms to the output data to plot density or color gradients to the output

data.

Figure 14. EOM Full Eye Capture Readout

To manually control the EOM vertical range, remove scaling control from the state machine then select the

desired range:

Channel Reg 0x2C[6]

→ 0 (see Table 3).

Table 3. Eye Opening Monitor Vertical Range Settings

CH REG 0x11[7:6] VALUE

EOM VERTICAL RANGE [mV]

2’b00

±100

2'b01

±200

2'b10

±300

2'b11

±400

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