TLK2501 Datasheet, PDF (11/25 Pages) Texas Instruments – 1.5 TO 2.5 GBPS TRANSCEIVER

TLK2501
1.5 TO 2.5 GBPS TRANSCEIVER
SLLS427D − AUGUST 2000 − REVISED JULY 2003
detailed description (continued)
loss of signal detection
The TLK2501 has a loss of signal detection circuit for conditions where the incoming signal no longer has a
sufficient voltage level to keep the clock recovery circuit in lock. The signal detection circuit is intended to be
an indication of gross signal error conditions, such as a detached cable or no signal being transmitted, and not
an indication of signal coding health. The TLK2501 reports this condition by asserting, the RX_DV/LOS, RX_ER
and RXD[0:15] all to a high state. As long as the signal is above 200 mV in differential magnitude, the LOS circuit
does not signal an error condition.
power down mode
When the ENABLE pin is deasserted low, the TLK2501 will go into a power down mode. In the power down
mode, the serial transmit pins (DOUTTXP, DOUTTXN), the receive data bus pins (RXD[0:15]), and RX_ER will
go into a high-impedance state. In the power-down mode the RX_DV/LOS pin acts as an output of the signal
detection circuit which remains active. If the signal detection circuit detects a valid differential signal amplitude
of >200 mV on each of the serial receive pins (DINRXP, DINRXN), RX_DV/LOS is driven high. If no signal of
sufficient amplitude is detected, the signal detection circuit will indicate a loss of signal by driving RX_DV/LOS
low. In the power-down condition, the signal detection circuit draws less than 5 mW.
synchronization and initialization
The TLK2501 has a synchronization-state machine which is responsible for handling link initialization and
synchronization. Upon power up or reset, the state machine enters the acquisition (ACQ) state and searches
for IDLE. Upon receiving three consecutive IDLEs or carrier extends, the state machine enters the
synchronization (SYNC) state. If, during the acquisition process, the state machine receives valid data or an
error propagation code, it immediately transitions to the SYNC state. The SYNC state is the state for normal
device transmission and reception. The initialization and synchronization state diagram is provided in Figure 6.
Invalid Code
Word Received
Power-Up/Reset
3 Invalid Code
Words Received
ACQ
(Link Acquisition)
3 Consecutive Valid IDLEs or Carrier Extends,
or
1 Valid Data or Error Propagation
Loss of Link
Link Established
Valid Code
Word Received
CHECK
(Look for Valid Code)
1 Invalid Code
Word Received
Link in Question
SYNC
(Normal Operation)
Link Re-established
4 Consecutive Valid Code Words Received
Figure 6. Initialization and Synchronization State Diagram
• POST OFFICE BOX 655303 DALLAS, TEXAS 75265
11