
XRT84L38
277
REV. 1.0.1
OCTAL T1/E1/J1 FRAMER
below demonstrates settings of the Slip Buffer Receive Synchronization Direction bit of the Slip Buffer Control
Register.
SLIP BUFFER CONTROL REGISTER (SBCR) (INDIRECT ADDRESS = 0XN0H, 0X16H)
If the Slip Buffer is in bypass mode, the Receive Payload Data is routed to the Receive Payload Data Output
Interface from the Receive Framer Module directly. The Recovered Line Clock is used to carry the Receive
Payload Data all the way from the LIU interface, to the Receive Framer Module and eventually output through
the Receive Serial Data output pin. The Receive Serial Clock signal is therefore an output using the Recovered
Receive Line Clock as timing source. The Receive Single-Frame Synchronization signal is also output in Slip
Buffer bypass mode.
If the Slip Buffer is enabled, the Receive Payload Data is latched into the Elastic Store using the Recovered
Receive Line Clock. The local Terminal Equipment supplies a free-running 2.048MHz clock to the Receive
Serial Clock pin to latch the Receive Payload Data out from the Elastic Store. Since the Recovered Receive
Line Clock and the Receive Serial Clock are coming from different timing sources, the Slip Buffer will gradually
fill or empty. If the elastic buffer either fills or empties, a controlled slip will occur. If the buffer empties and a
read occurs, then a full frame of data will be repeated and a status bit will be updated. If the buffer fills and a
write comes, then a full frame of data will be deleted and another status bit will be set. A detailed description of
the Elastic Buffer can be found in later sections. In this mode, the Receive Single-Frame Synchronization
signal can be either input or output depending on the settings of the Slip Buffer Receive Synchronization
Direction bit of the Slip Buffer Control Register.
If the Slip Buffer is put into a FIFO mode, it is acting like a standard First-In-First-Out storage. A fixed READ
and WRITE latency is maintained in a programmable fashion controlled by the FIFO Latency Register
(FIFOLR). The local Terminal Equipment supplies a 2.048MHz clock to the Receive Serial Clock pin to latch
the Receive Payload Data out from the FIFO. However, it is the responsibility of the user to phase lock the
input Receive Serial Clock to the Recovered Receive Line Clock to avoid either over-run or under-run of the
FIFO. In this mode, the Receive Single-Frame Synchronization signal can be either input or output depending
on the settings of the Slip Buffer Receive Synchronization Direction bit of the Slip Buffer Control Register.
The following table summaries the input or output nature of the Receive Serial Clock and Receive Single-
Frame Synchronization signals for different Slip Buffer settings.
B
IT
N
UMBER
B
IT
N
AME
B
IT
T
YPE
B
IT
D
ESCRIPTION
2
Slip Buffer
Receive
Synchronization
Direction
R/W
0 - The Receive Single-Frame Synchronization signal (RxSync_n) is an output
if the Slip Buffer is not in bypass mode.
1 - The Receive Single-Frame Synchronization signal (RxSync_n) is an input
if the Slip Buffer is not in bypass mode.
R
ECEIVE
T
IMING
S
OURCE
R
X
S
ER
C
LK
_
N
R
X
S
YNC
_
N
Slip Buffer Synchronization
Direction Bit = 0
Slip Buffer Synchronization
Direction Bit = 1
Slip Buffer Bypassed
Output
Output
Output
Slip Buffer Enabled
Input
Output
Input
Slip Buffer Acts as FIFO
Input
Output
Input