Datasheet

TLK3101
2.5 Gbps to 3.125 Gbps TRANSCEIVER
SCAS649B − AUGUST 2000 − REVISED JANUARY 2008
13
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
Terminal Functions (Continued)
signal (continued)
TERMINAL
TYPE
DESCRIPTION
NAME NO.
TYPE
DESCRIPTION
PREM 56 Input
‡
Preemphasis control. Selects the amount of preemphasis to be added to the high speed data output drivers.
Left low or unconnected, 5% of pre-emphasis is added. Pulled high, 20% of preemphasis is added.
RX_ER/
PRBS_PASS
29 Output
†
Receive error. When RX_ER and RX_DV/LOS are asserted, indicates that an error was detected
somewhere in the frame presently being output on the receive data bus. When RX_ER is asserted and
RX_DV/LOS is deasserted, indicates that carrier extension data is being presented. RX_ER goes to high
impedance state during power-on reset.
When PRBSEN= low (deasserted), this pin is used to indicate receive error (RX_ER). When PRBSEN = high
(asserted), this pin indicates status of the PRBS test results (high=pass).
RX_DV/
LOS
30 Output
†
Receive data valid. RX_DV/LOS is output by the transceiver to indicate that recovered and decoded data is
being output on the receive data bus. RX_DV/LOS is asserted continuously from the first recovered word of
the frame through the final recovered word and is deasserted prior to the first rising edge of RX_CLK that
follows the final word. RX_DV/LOS is in high-impedance state during power-on reset.
If, during normal operation, the differential signal amplitude on the serial receive pins is below 200 mV,
RX_DV/LOS is asserted high along with RX_ER and the receive data bus to indicate a loss of signal
condition. If the device is in power-down mode, RX_DV/LOS is the output of the signal detect circuit and is
asserted low when a loss of signal condition is detected.
TX_EN 20 Input
‡
Transmit enable. TX_EN in combination with TX_ER indicates the protocol device is presenting data on the
transmit data bus for transmission. TX_EN must be high with the first word of the preamble and remain
asserted while all words to be transmitted are presented on the transmit data bus. TX_EN must be negated
prior to the first rising edge of GTX_CLK following the final word of a frame.
TX_ER 22 Input
‡
Transmit error coding. When TX_ER and TX_EN are high, indicates that the transceiver generates an error
somewhere in the frame presently being transferred. When TX_ER is asserted and TX_EN is deasserted,
indicates the protocol device is presenting carrier extension data. When TX_ER is deasserted with TX_EN
asserted, indicates that normal data is being presented.
†
Hi-Z on power-up
‡
Internal pull-down
test
TERMINAL
TYPE
DESCRIPTION
NAME NO.
TYPE
DESCRIPTION
ENABLE 24 Input
§
Device enable. When this pin is held low, the device is placed in power-down mode. Only the signal detect
circuit on the serial receive pair is active. When asserted high, the transceiver goes into power-on reset
before beginning normal operation.
LOOPEN 21 Input
‡
Loop enable. When LOOPEN is high, the internal loopback path is activated. The transmitted serial data is
directly routed internally to the inputs of the receiver. This provides a self-test capability in conjunction with
the protocol device. The DOUTTXP and DOUTTXN outputs are held in a high-impedance state during the
loopback test. LOOPEN is held low during standard operational state with external serial outputs and inputs
active.
PRBSEN 26 Input
‡
PRBS test enable. When asserted high results of pseudorandom bit stream (PRBS) tests can be monitored
on the RX_ER/PRBS_PASS pin. A high on PRBS_PASS indicates that valid PRBS is being received.
TESTEN 27 Input
‡
Test mode enable. This pin should be left unconnected or tied low.
‡
Internal pulldown
§
Internal pullup