
XRT84L38
220
OCTAL T1/E1/J1 FRAMER
REV. 1.0.1
Equipment when the Slip Buffer is bypassed and the Recovered Receive Line Clock is timing source of the
Receive section.
5.1.2.2
Connect the Receive Payload Data Output Interface block to the Local Terminal
Equipment if the Slip Buffer is enabled
By setting the Slip Buffer Enable [1:0] bits of the Slip Buffer Control Register to 01, the framer includes the two-
frame Elastic Buffer into its data path. The Receive Framer Module routes the Receive Payload Data to the
Elastic Buffer first. The Receive Payload Data is then presented to the Receive Payload Data Output Interface.
The XRT84L38 uses the Recovered Receive Line Clock internally to clock in the Receive Payload Data into
the Elastic Buffer. The Terminal Equipment should provide a 1.544MHz clock to the Receive Serial Clock input
pin to latch data out from the Elastic Buffer.
The Recovered Receive Line Clock and the Receive Serial Clock are generated from two different timing
sources. That is, the Recovered Receive Line Clock is originating from a remote site while Receive Serial
Clock generating by a local oscillator. Any mismatch in frequencies of these two clocks will result in the Slip
Buffer to gradually fill or deplete.
Overtime, the Elastic Buffer either fills or empties completely. Once that happened, a controlled slip by the
XRT84L38 will occur. The Receive Slip Buffer Slip bit of the Slip Buffer Status Register (SBSR) is set to 1.
If the buffer empties and a read occurs, then a full frame of data will be repeated and the Receive Slip Buffer
Empty bit of the Slip Buffer Status Register (SBSR) will be forced HIGH. If the buffer fills and a write comes,
then a full frame of data will be deleted and the Receive Slip Buffer Full bit of the Slip Buffer Status Register
(SBSR) will be forced HIGH.
The following table demonstrates settings of the Receive Slip Buffer Slip bit, Receive Slip Buffer Empty bit and
Receive Slip Buffer Full bit of the Slip Buffer Status Register.
F
IGURE
44. W
AVEFORMS
OF
THE
S
IGNALS
C
ONNECTING
THE
R
ECEIVE
P
AYLOAD
D
ATA
O
UTPUT
I
NTERFACE
BLOCK
TO
THE
LOCAL
T
ERMINAL
E
QUIPMENT
WHEN
THE
S
LIP
B
UFFER
IS
B
YPASSED
AND
THE
R
ECOVERED
L
INE
C
LOCK
IS
THE
T
IMING
S
OURCE
OF
THE
R
ECEIVE
S
ECTION
C
RxSerClk
RxSer
RxSync(input)
RxSync(output)
RxTSClk
RxTSb[4:0]
RxTSb[0]/RxSig
RxTSClk
RxTSb[2]/RxTSb
RxTSb[1]/RxFrTD
c1 c2 c3 c4 c5
c1 c2 c3 c4 c5
c1 c2 c3 c4 c5
c1 c2 c3 c4 c5
8
7
6
5
4
3
2
1
A B
D
C
A B
D
C
A B
D
C
A B
D
Input Data
Input Data
Timeslot 16
Timeslot 0
Timeslot 5
Timeslot 6
Timeslot #0
Timeslot #5
Timeslot #6
Timeslot #16