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QuadFALC
TM
PEF 22554 E
Functional Description T1/J1
Data Sheet
174
Rev. 1.2, 2006-01-26
Figure 67 gives an idea of operation of the 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 by the
interrupt status bits ISR3.RSP and ISR3.RSN (ISR3_T).
Figure 67
The Receive Elastic Buffer as Circularly Organized Memory
5.2
Transmit Path in T1/J1 Mode
An overview about the transmit path of one channel of the QuadFALC
special T1/J1 functionalities are described in this chapter.
5.2.1
Transmit Elastic Buffer (T1/J1)
The transmit elastic store with a size of max. 386 bit (two frames) serves as a temporary store for the PCM data
to adapt the system clock (SCLKX) to the internally generated clock for the transmit data, and to retranslate time
slot structure used in the system to that of the line side. Its optimal start position is initiated when programming the
transmit time slot offset values. A difference in the effective data rates of system side and transmit side lead to an
overflow or underflow of the transmit memory. Thus, errors in data transmission to the remote end occur. This error
condition (transmit slip) is reported to the microprocessor by interrupt status registers. The received bit stream
10
Short buffer
Not recommended,
Recommended: SYPR =output
(usage of the RFM with CMR2.IRSP
= 0
B)
Yes
01
1 frame
Yes
00
2 frames
Enabled
Yes
Table 48
Receive Buffer Operation Modes (T1/J1) (cont’d)
SIC1.RBS(1:0)
Buffer Size
TS Offset Programming
(RC(1:0)) + SYPR = input
Slip Performing
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