GX3146 Datasheet, PDF(27/46 Page) Semtech Corporation – Crosspoint Switch with Trace Equalization and Output De-emphasis

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GX3146 Datasheet, PDF (27/46 Pages) Semtech Corporation – Crosspoint Switch with Trace Equalization and Output De-emphasis

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The CDR integrated in each Rx block can independently lock to data at rates of 270Mb/s,

1.485Gb/s and 2.97Gb/s. Other rates up to 3Gb/s can be analyzed by providing an

external clock signal of 2x, 4x, or 22x the desired bit rate, with a maximum external

clock frequency of 6GHz. Note that retiming is not possible when using an external

clock signal for the Rx block. The external clock must be synchronous with any data to

be checked and the RX0_PRBS_CHK_MODE bits must be set to a value of '01'. The two

pattern checker âRxâ blocks in the GX3146 can each independently check PRBS 27-1,

PRBS 215-1, and PRBS 223-1 data patterns.

Table 4-6: Rx External Clocks

RX0

EXT_CLK0 (R35)

EXT_CLK0 (T35)

RX1

EXT_CLK1 (AJ15)

EXT_CLK1 (AH15)

The error checking modes are selected by the RX0_PRBS_CHK_MODE bits and the

RX1_PRBS_CHK_MODE bits (addresses 0x804h and 0x810h respectively).

Table 4-7: Checking Modes

RX0_PRBS_CHK_MODE[1:0] (binary)

Input Mode

10 or 11

Check data sampled at neutral phase

Check data sampled at adjustable phase

Compare nominally sampled data with phase offset

data (allows eye monitoring of arbitrary patterns)

The pattern checker will check for the PRBS pattern specified by the

RX0_PRBS_POLYNOMIAL and RX1_PRBS_POLYNOMIAL bits (addresses 0x803h

and 0x811h respectively).

The PRBS checkers are enabled by the RX0_PRBS_ENABLE and RX1_PRBS_ENABLE

bits (register address 0x81Dh[1:0]).

Table 4-8: Checked Patterns

RX0_PRBS_POLYNOMIAL[1:0] (binary)

Pattern Checked

PRBS7

PRBS15

PRBS23

The incident data can be inverted before checking by setting the corresponding

RX0_INVERT_PRBS_IN or RX1_INVERT_PRBS_IN bit (address 0x803h[2:2] and

0x811h[2:2]) to '1'.

The number of words to be compared is selectable via the corresponding

RX0_PRBS_BER_TIME and RX1_PRBS_BER_TIME bits (registers 0x80Ah and

0x817h).

GX3146 146 x 146 3.5Gb/s Crosspoint

Final Data Sheet Rev. 2

GENDOC-056075 March 2013

www.semtech.com

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