CS61577-IP1 datasheet(34/44 Pages) ETC

34 / 44 page

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-

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

µF DC blocking capacitor.

LINE INTERFACE EVALUATION BOARD

DS40DB3

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