CS61305A-IL1 Cirrus Logic, Inc., CS61305A-IL1 Datasheet - Page 15

• Manufacturer Part Number: CS61305A-IL1
• Description: T1/E1 line interface
• Manufacturer: Cirrus Logic, Inc.

Local Loopback
Local loopback is selected by taking LLOOP, pin
27, high or by setting the LLOOP register bit via
the serial interface.
The local loopback mode takes clock and data
presented on TCLK, TPOS, and TNEG (or
TDATA), and outputs it at RCLK, RPOS and
RNEG (or RDATA). Inputs to the transmitter are
still transmitted on TTIP and TRING, unless
TAOS has been selected in which case, AMI-
coded continuous ones are transmitted at the
TCLK frequency. The receiver RTIP and RRING
inputs are ignored when local loopback is in ef-
fect. The jitter attenuator is not in the local loop
back path.
Remote Loopback
Remote loopback is selected by taking RLOOP,
pin 26, high or by setting the RLOOP register bit
via the serial interface.
In remote loopback, the recovered clock and data
input on RTIP and RRING are sent through the
jitter attenuator and back out on the line via TTIP
and TRING. Selecting remote loopback overrides
any TAOS request (see Table 7). The recovered
Notes: 1. X = Don’t Care. The identified All Ones Select
DS157PP3
RLOOP
Signal
Input
0
0
1
Table 7. Interaction of RLOOP with TAOS
2. Logic 1 indicates that Loopback or All Ones
Signal
TAOS
Input
input is ignored when the indicated loopback is
in effect.
option is selected.
X
0
1
RTIP & RRING RTIP & RRING (RCLK)
TTIP & TRING
Source of
Data for
TDATA
all 1s
TTIP & TRING
Source of
Clock for
TCLK
TCLK
incoming signals are also sent to RCLK, RPOS
and RNEG (or RDATA). A remote loopback oc-
curs in resp onse to RLOOP going high.
Simultaneous selection of local and remote loop-
back modes is not valid (see Reset).
In the Extended Hardware Mode the transmitted
data is looped before the AMI/B8ZS/HDB3 en-
coder/decoder during remote loopback so that the
transmitted signal matches the received signal,
even in the presence of received bipolar viola-
tions. Data output on RDATA is decoded,
however, if RCODE is low.
Driver Performance Monitor
To aid in early detection and easy isolation of
non-functioning links, the IC is able to monitor
transmit drive performance and report when the
driver is no longer operational. This feature can
be used to monitor either the device’s perform-
ance or the performance of a neighboring driver.
The driver performance monitor indicator is nor-
mally low, and goes high upon detecting a driver
failure.
The driver performance monitor consists of an ac-
tivity detector that monitors the transmitted signal
when MTIP is connected to TTIP and MRING is
connected to TRING. DPM will go high if the
absolute difference between MTIP and MRING
does not transition above or below a threshold
level within a time-out period. In the Host Mode,
DPM is available from both the register and pin
11.
Whenever more than one line interface IC resides
on the same circuit board, the effectiveness of the
driver performance monitor can be maximized by
having each IC monitor performance of a neigh-
boring IC, rather than having it monitor its own
performance.
CS61305A
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