CDB61574 Cirrus Logic, Inc., CDB61574 Datasheet - Page 15

• Manufacturer Part Number: CDB61574
• Description: T1/e1 LINE Interface
• Manufacturer: Cirrus Logic, Inc.

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.
Alarm Indication Signal
In the Extended Hardware Mode, the receiver sets
the output pin AIS high when less than 3 zeros
are detected out of 2048 bit periods.
Line Code Encoder/Decoder
In the Extended Hardware Mode, three line codes
are available: AMI, B8ZS and HDB3. The input
to the encoder is TDATA. The outputs from the
decoder are RDATA and BPV (Bipolar Violation
Strobe). The encoder and decoder are selected
using the LEN2, LEN1, LEN0, TCODE and
RCODE pins as shown in Table 8.
DS155PP2
Selection)
Selection)
(Receiver
(Transmit
Decoder
Encoder
RCODE
TCODE
Table 8. Encoder/Decoder Selection
HIGH
HIGH
LOW
LOW
Decoder
Encoder
HDB3
HDB3
000
AMI Decoder
AMI Encoder
LEN 2/1/0
Encoder
Decoder
010-111
B8ZS
B8ZS
Parallel Chip Select
In the Extended Hardware Mode, PCS can be
used to gate the digital control inputs: TCODE,
RCODE, LEN0, LEN1, LEN2, RLOOP, LLOOP
and TAOS. Inputs are accepted on these pins only
when PCS is low and will immediately change
the operating state of the device. Therefore, when
cycling PCS to update the operating state, the
digital control inputs should be stable for the en-
tire PCS low period. The digital control inputs are
ignored when PCS is high
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 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. Note that a CS61577 can not be
used to monitor a CS61574 due to output stage
differences.
CS61577
15