CDB61318 Cirrus Logic, Inc., CDB61318 Datasheet - Page 4

• Manufacturer Part Number: CDB61318
• Description: T1/e1 Line Interface Units
• Manufacturer: Cirrus Logic, Inc.

4. RECEIVE CIRCUIT
The receive signal is input at either the Receive
binding posts (J4, J10) or the Receive bantam jack.
The receive signal is transformer coupled to the
CS61318 through the transformer T1.
The receive line is terminated by resistors R1-R2 to
provide impedance matching and receiver return
loss. They are socketed so the values may be
changed according to the application. The evalua-
tion board is supplied from the factory with 60
resistors for terminating 120
and 37.5
cables. Capacitor C3 provides an AC ground refer-
ence for the differential input.
The recovered clock and data signals are available
on BNC outputs labeled RCLK, RPOS, and RNEG.
In Hardware and Host mode (with coder mode dis-
abled), data is available on the RPOS and RNEG
BNC. With coder mode enabled, data is available
on the RDATA BNC output in unipolar format and
bipolar violations are reported on the RNEG BNC
connector.
5. REFERENCE CLOCK
The CDB61318 requires an E1 reference clock for
operation. This clock can be supplied by either a
quartz crystal or an external reference. The evalua-
tion board is supplied from the factory with a
quartz crystal. In the case that both the external ref-
erence and the quartz crystal are applied, the exter-
nal reference takes precedence.
4
resistors for terminating 75
LATN1
OFF
OFF
ON
ON
twisted-pair lines,
coaxial
LATN2
Table 1. LATN Settings
OFF
OFF
ON
ON
5.1
A quartz crystal may be inserted at socket Y1. The
quartz crystals operate at 4X the frequency of oper-
ation: 8.192 MHz.
5.2
An external reference of 2.048 MHz may be provid-
ed at the REFCLK BNC input. Header HDR7 must
be jumpered in the "MCLK" position to provide con-
nectivity to the MCLK pin of the CS61318.
5.3
The four-LED pack D1 indicates signal states on
LATN1, LATN2, LOS and NLOOP. The LOS
LED indicator illuminates when the line interface
receiver has detected a loss of signal. The NLOOP
LED indicates if Network Loopback is in opera-
tion. The LATN1/LATN2 LED’s indicate the at-
tenuation level of the received signal; reading how
much the incoming signal is below the nominal ex-
pected signal level. See Table 1 for details.
6. BUFFERING
Buffer U2 provides additional drive capability for
the SW1 and Host mode connections. The buffer
outputs are filtered with an (optional) RC network
(not initially populated) to reduce the transients
caused by buffer switching.
7. TRANSFORMER SELECTION
The evaluation board is supplied from the factory
with PE-64936 (1:1), PE-65351 (1:2) and T-1229
(1:1.58) transformers by Pulse Engineering. The
socket T1 on the board is for receive side trans-
former and T2 is for the transmit side. Please see
Table 2 for details on transformers selection.
Quartz Crystal
External Reference
LED Indicators
Attenuation Level (dB)
19.5
28.5
9.5
0
CDB61318
DS441DB1