
Data Sheet
69
Rev. 1.0, 2005-06-02
OctalLIU
TM
PEF 22508 E
Functional Description
In “one frame” or short buffer mode the delay through the receive buffer is reduced to an average delay of 128 or
46 bits. In bypass mode the time slot assigner is disabled. Slips are performed in all buffer modes except the
bypass mode. After a slip is detected the read pointer is adjusted to one half of the current buffer size.
Figure 28 gives an idea of operation of the dual receive elastic buffer: A slip condition is detected when the write
pointer (W) and the read pointer (R) of the memory are nearly coincident, i.e. the read pointer is within the slip
limits (S +, S –). If a slip condition is detected, a negative slip (one frame or one half of the current buffer size is
skipped) or a positive slip (one frame or one half of the current buffer size is read out twice) is performed at the
system interface, depending on the difference between RCLK and the current working clock of the receive
backplane interface. I.e. on the position of pointer R and W within the memory. A positive/negative slip is indicated
in the interrupt status bits ISR3.RSP and ISR3.RSN.
Figure 28
The Receive Elastic Buffer as Circularly Organized Memory
3.8
Additional Receiver Functions
3.8.1
Error Monitoring and Alarm Handling
The following error monitoring and alarm handling is supported by the OctalLIU
TM:
Loss-Of-Signal: Detection and recovery is flagged by bit LSR0.LOS and ISR2.LOS.
Transmit Line Shorted: Detection and release is flagged by bit LSR1.XLS and ISR1.XLSC
Transmit Ones-Density: Detection and release is flagged by bit LSR1.XLO and ISR1.XLSC
Limits for Slip Detection (mode dependent)
Read Pointer (System Clock controlled)
Write Pointer (Route Clock controlled)
R’
S+, S-
R
:
W:
Frame 2 Time Slots
S-
R
Frame 1 Time Slots
Moment of Slip Detection
ITD10952
W
S+
Slip