PEB 22554
Functional Description T1 / J1
Semiconductor Group
222
09.98
Frame alignment between system frame and receive route frame
Reporting and controlling of slips
Controlled by special signals generated by the receiver, the unipolar bit stream is
converted into bit-parallel, time-slot-serial data which is circularly written to the elastic
buffer using internally generated Receive Route Clock (RCLK).
Reading of stored data is controlled by the System Clock sourced by SCLKR or by the
receive jitter attenuator and the Synchronous Pulse (SYPR) in conjunction with the
programmed offset values for the receive time-slot/clock-slot counters. After conversion
into a serial data stream, the data is given out via port RDO. If the receive buffer is
bypassed programming of the time-slot offset is disabled and data is clocked off with
RCLK instead of SCLKR.
The 24 received time-slots are translated into the 32 system time-slots in two different
channel translation modes (FMR1.CTM). Unequipped time-slots will be set to ‘FF
H
’.
Refer to
table 17
.
In one frame or short buffer mode the delay through the receive buffer is reduced to an
average delay of 96 or 48 bits. In bypass mode the time-slot assigner is disabled. In this
case SYPR programmed as input is ignored. Slips will be 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.
The following table gives an overview of the receive buffer operating mode .
Figure 49
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
1) In bypass mode the clock provided on pin SCLKR is ignored. Clocking is done with RCLK.
Buffer Size
(SIC1.RBS1/0)
TS Offset program.
(RC1/0) + SYPR = input
Slip perform.
bypass
1)
disabled
no
short buffer
not recommended,
recom. SYPR = output
yes
1 frame
not recommended,
recom. SYPR = output
yes
2 frames
enabled
yes