xrt59l921 Exar Corporation, xrt59l921 Datasheet - Page 18

• Manufacturer Part Number: xrt59l921
• Description: Xrt59l921 -twenty-one Channel E1 Line Interface Unit
• Manufacturer: Exar Corporation

XRT59L921
TWENTY-ONE CHANNEL E1 LINE INTERFACE UNIT
In general, if the XRT59L921 samples a “1” on the TxPOS_n input pin, then the Transmit Section of the device
will ultimately generate a positive polarity pulse via the TTIP_n and TRing_n output pins (across a 1:2 trans-
former). Conversely, if the XRT59L921 samples a “1” on the TxNEG_n input pin, then the Transmit Section of
the device will ultimately generate a negative polarity pulse via the TTIP_n and TRing_n output pins (across a
1:2 transformer).
The user can configure a given channel (within theXRT59L921) to operate in the Clockless mode by doing the
following:
•
•
•
The Transmit Driver for each Channel_n (within the XRT59L921) can be shut off. To activate this feature,
Connect the TxCLK_n input pin to a logic "0" (e.g. GND) and continue to apply data via the TxPOS_n and
TxNEG_n input pins.
F
PINS
1.2.1
1.2.2
IGURE
Not applying a clock signal to the TxClk_n input, and pulling this pin to VDD.
By applying RZ (Return to Zero) data to the TxPOS_n and TxNEG_n input pins, as illustrated below.
If TxClk_n is grounded and RZ data is applied to TPOS and TNEG, the transmitter will be
powered down and tri-stated.
4. I
Operating the Transmitter in the Clockless Mode
Shutting off the Transmiter
LLUSTRATION ON HOW THE
TxPOS_n
TxNEG_n
TClk_n
T
su
XRT59L921 S
T
ho
AMPLES THE DATA ON THE
16
T
X
POS_
N AND
T
X
NEG_
REV. 1.2.1
N INPUT