CS61574-IL Cirrus Logic, Inc., CS61574-IL Datasheet - Page 34

• Manufacturer Part Number: CS61574-IL
• Description: Interface, T1/E1 Line Interface
• Manufacturer: Cirrus Logic, Inc.

Performance Monitor alarm. The LED labeled
LOS illuminates when the line interface receiver
has detected a loss of signal.
Extended Hardware Mode
In the Extended Hardware operating mode, the
line interface is configured using DIP switch S2.
The digital control inputs to the device selected
by S2 include: transmit all ones (TAOS), local
loopback (LLOOP), remote loopback (RLOOP),
transmit line length selection (LEN2, LEN1,
LEN0), transmit line code (TCODE), and receive
line code (RCODE). Closing a DIP switch (mov-
ing it towards the S2 label) sets the device control
pin of the same name to logic 1 (+5 Volts). Note
that the TCODE and RCODE options are active
low and are enabled when the switch is moved
away from the S2 label. The parallel chip select
input PCS is tied to ground in Extended Hard-
ware mode to enable the device to be reconfig-
ured when S2 is changed. In addition, the host
processor interface connector JP1 should not be
used in Extended Hardware mode.
Two LED status indicators are provided in Ex-
tended Hardware mode. The LED labeled DPM
(AIS) illuminates when the line interface detects
the receive blue alarm (AIS). The LED labeled
LOS illuminates when the line interface receiver
has detected a loss of signal.
Host Mode
In the Host operating mode, the line interface is
configured using a host processor connected to
the serial interface port JP1. The S2 switch posi-
tion labeled CLKE selects the active edge of
SCLK and RCLK. Closing the CLKE switch se-
lects RPOS and RNEG to be valid on the falling
edge of RCLK and SDO to be valid on the rising
edge of SCLK as required by the CS2180B T1
framer.
All other DIP switch positions on S2 should be
open (logic 0) to prevent shorting of the serial in-
34
terface signals. Resistor R15 is a current limiting
resistor that prevents the serial interface signals
from being shorted directly to the +5 Volt supply
if any S2 switch, other than CLKE, is closed.
Jumper JP3 should be out so the INT pin may be
externally pulled-up at the host processor inter-
rupt pin.
Two LED status indicators are provided in Host
mode. The LED labeled DPM (AIS) illuminates
when the line interface asserts the Driver Per-
formance Monitor alarm. The LED labeled LOS
illuminates when the line interface receiver has
detected a loss of signal.
Manual Reset
A manual reset circuit is provided that can be
used in Hardware and Extended Hardware
modes. The reset circuit consists of S1, R4, R16,
C4, D8, and D9. Pressing switch S1 forces both
LLOOP and RLOOP to a logic 1 and causes a
reset. A reset is only necessary for the CS61534
device to calibrate the center frequency of the re-
ceiver clock recovery circuit. All other line inter-
face units use a continuously calibrated clock re-
covery circuit that eliminates the reset require-
ment.
TRANSMIT CIRCUIT
The transmit clock and data signals are supplied
on BNC inputs labeled TCLK, TPOS(TDATA),
and TNEG. In the Hardware and Host operating
modes, data is supplied on the TPOS(TDATA)
and TNEG connectors in dual NRZ format. In the
Extended Hardware operating mode, data is sup-
plied in NRZ format on the TPOS(TDATA) con-
nector and TNEG is not used.
The transmitter output is transformer coupled to
the line through a transformer denoted as T1 in
Figure 1. The signal is available at the TTIP and
TRING binding posts. Capacitor C5 is the recom-
mended 0.47 F DC blocking capacitor.
LINE INTERFACE EVALUATION BOARD
DS40DB3