ONET1130EC datasheet(23/64 Pages) TI2

23 / 64 page

ONET1130EC

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SLLSEJ3A – JUNE 2015 – REVISED JULY 2015

Feature Description (continued)

8.3.1.5 DC Offset Cancellation and Cross Point Control

The ONET1130EC transmitter has DC offset cancellation to compensate for internal offset voltages. The offset

cancellation can be disabled by setting TXOC_DIS = 1 (bit 2 of register 10).

The crossing point can be moved toward the one level by setting TXCPSGN = 1 (bit 7 of register 14) and it can

be moved toward the zero level by setting TXCPSGN = 0. The percentage of shift depends upon the register

settings of the transmitter cross-point adjustment bits TXCPADJ[0..6] (register 14).

8.3.1.6 Transmitter Loopback (Electrical Loopback)

The signal input to the TXIN+ and TXIN– pins can be looped back to the receiver output after the retimer as

shown in Figure 38 by setting TX_LBMUX = 1 (bit 0 of register 2). Loopback from the receiver input to the

transmitter output (optical loopback) can be enabled at the same time.

If it is desired to loopback the signal input to the TXIN+ and TXIN– pins to the receiver output with the CDR

disabled then the transmit CDR must be disabled and bypassed by setting TXCDR_DIS = 1 (bit 4 of register 10)

and the receiver CDR must also be disabled and bypassed by setting RXCDR_DIS =1 (bit 4 of register 4).

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