
XRT84L38
183
REV. 1.0.1
OCTAL T1/E1/J1 FRAMER
When the Transmit Fractional T1 Input Enable bit is equal to one, the TxTSb[0]_n bit becomes the Transmit
Fractional T1 Input signal (TxFrTD_n). This input pin carries Fractional T1 Input data to be inserted into the
outbound DS1 data stream. The Fraction T1 Input Interface allows certain time-slots of outbound DS1 data
stream to have a different source other than the local Terminal Equipment. Function of the Fractional T1 Input
signal will be discussed in details in later sections.
When the Transmit Fractional T1 Input Enable bit is equal to one, the TxTSb[1]_n bit becomes the Transmit
Signaling Data Input signal (TxSig_n). These input pins can be used to insert robbed-bit signaling data into the
outbound DS1 frame. Function of the Transmit Signaling Data Input signal will be discussed in details in later
sections.
When the Transmit Fractional T1 Input Enable bit is equal to one, the TxTSb[2]_n bit serially outputs all five-bit
binary values of the Time Slot number (0-23) being accepted and processed by the Transmit Payload Data Input
Interface block of the framer. MSB of the binary value is presented first and the LSB is presented last.
When the Transmit Fractional T1 Input Enable bit is equal to one, the TxTSb[3]_n bit becomes the Transmit
Overhead Synchronization Pulse (TxOHSync_n). These pins can be used to output an Overhead
Synchronization Pulse that indicates the first bit of each DS1multi-frame. Function of the Transmit Overhead
Synchronization Output signal will be discussed in details in later sections.
The TxTSb[4]_n bit is not multiplexed.
The table below shows functionality of the TxTSb[3:0] bits when the Transmit Fractional T1 Input bit is set to
different values.
T
ABLE
37: T
HE
T
X
TS
B
[3:0]
BITS
WHEN
THE
T
RANSMIT
F
RACTIONAL
T1 I
NPUT
BIT
IS
SET
TO
DIFFERENT
VALUES
The Transmit Time-slot Indicator Clock signal (TxTSClk_n) is a multi-function output pin. When configured to
operate in normal condition (that is, when the Transmit Fractional T1 Input Enable bit is equal to zero), the
TxTSClk_n is a 192KHz clock that pulses HIGH for one DS1 bit period whenever the Transmit Payload Data
Input Interface block is accepting the LSB of each of the twenty-four time slots. The local Terminal Equipment
should use this clock signal to sample the TxTSb[0] through TxTSb[4] bits and identify the time-slot being
processed via the Transmit Section of the framer.
When the Transmit Fractional T1 Input Enable bit is equal to one, the TxTSClk_n will output gaped fractional DS1
clock at time-slots where Fractional T1 Input data is present. This clock can be used by Terminal Equipment to
clock out Fractional DS1 payload data at rising edge of the clock. The framer will then input Fractional DS1
payload data using falling edge of the clock. Otherwise, this pin can be configured as a clock enable signal to
Transmit Fractional DS1 Input signal (TxFrTD_n) if the framer is set accordingly. In this way, Fractional DS1
payload data is clocked into the framer using un-gaped Transmit Serail Input Clock (TxSerClk_n). A detailed
discussion of the Fractional DS1 Payload Data Input Interface can be found in later sections.
Both the Transmit Time-slot Indicator Clock (TxTSClk_n) and the Transmit Time-slot Indication Bits
(TxTSbb[4:0]_n) are output signals in normal 1.544Mbit/s Back-plane mode regardless of the timing source of the
Transmit Section of framer.
4.1.2.1
Connect the Transmit Payload Data Input Interface block to the Local Terminal Equipment
if Transmit Timing Source = TxSerClk_n
By setting the Transmit Timing Source [1:0] bits of the Clock Select Register to 01, the TxSerClk_n input signal is
configured to be the timing source for the Transmit section of the framer. The Terminal Equipment should supply
an external free-running clock with frequency of 1.544MHz to the TxSerClk_n input pin. The Transmit Single-
frame Synchronization signal and the Transmit Multi-frame Synchronization signal are inputs to the framer.
T
RANSMIT
F
RACTIONAL
T1 I
NPUT
B
IT
= 0
T
RANSMIT
F
RACTIONAL
T1 I
NPUT
B
IT
= 1
TxTSb[0]
Output
TxFrTD
Input
TxTSb[1]
Output
TxSig
Input
TxTSb[2]
Output
TxTS
Output
TxTSb[3]
Output
TxOHSync
Output