XRT59L91 Datasheet, PDF (9/28 Pages) Exar Corporation – Single-Chip E1 Line Interface Unit

Preliminary
XRT59L91
TxPOS
TxNEG
TClk
tSU
tHO
Figure 2. Illustration on how the XRT59L91 Device Samples the data on the
TXPOS and TXNEG input pins
In general, if the XRT59L91 device samples a “1” on the
TxPOS input pin, then the “Transmit Section” of the
device will ultimately generate a positive polarity pulse
via the TTIP and TRing output pins (across a 1:2
transformer). Conversely, if the XRT59L91 device
samples a “1” on the “TxNEG” input pin, then the
“Transmit Section” of the device will ultimately generate
a negative polarity pulse via the TTIP and TRing output
pins (across a 1:2 transformer).
B it
P e rio d
RZ Pulse width
should conform to
G .703 Tem plate
1.2.1 Operating the Transmitter in the
“Clockless” Mode
The user can configure the XRT59L91 device to oper-
ate in the “Clockless” mode by doing the following:
l Not applying a clock signal to the TXClk input,
and either pulling this pin to VDD or letting it float.
l By applying RZ (Return to Zero) data to the
TxPOS and TxNEG input pins, as illustrated
below.
No pulse is to be applied
in the second half of the
bit period
D a ta
1
1
0
1
1
0
1
TxPOS
TxNEG
T x C lk
No Activity in
TxClk Line
Figure 3. IIlustration on how the Terminal Equipment should apply data to the “Transmit Sec-
tion” of the XRT59L91 Device, when operating in the “Clockless” Mode
Rev. P2.00
9