CS61310-CL Cirrus Logic, Inc., CS61310-CL Datasheet - Page 9

• Manufacturer Part Number: CS61310-CL
• Description: Interface, T1 Line Interface Unit
• Manufacturer: Cirrus Logic, Inc.

2. THEORY OF OPERATION
The CS61310 Line Interface Unit is a fully integrat-
ed transceiver for T1 long haul applications. The
transmitter outputs all pulse shapes for T1 applica-
tions.
2.1
The CS61310 can be operated as a stand-alone
device with its interface in hardware mode (MODE
pin is low), or it can be operated by a microcontrol-
ler over a serial interface in host mode (MODE pin
is high). Host mode enables the use of additional
functionality, as described in the Serial Interface
section.
2.2
The CS61310 requires a reference clock for the re-
ceiver and the jitter attenuator. A 1.544 MHz exter-
nal clock can be input to MCLK, or a 4x crystal can
be connected to the on-chip oscillator. This fre-
quency reference should be within +32 ppm of the
nominal operating frequency. Jitter and wander on
the reference clock will degrade jitter attenuation
and receiver jitter tolerance. If MCLK is provided,
the crystal oscillator is ignored.
2.3
The transmitter accepts digital T1 input data and
drives appropriately shaped AMI (Alternate Mark
Inversion) pulses onto a transmission line through
a transformer. The transmit data (TPOS & TNEG
or TDATA) is sampled on the falling edge of the in-
put clock, TCLK.
The pulse shapes comply with FCC Part 68 Option
A (0 dB), Option B (-7.5 dB), Option C (-15 dB) or
(-22.5 dB) (see Table 1). Pulse shaping and signal
level are controlled by LBO1 and LBO2 pins in
hardware mode, or the LBO1 and LBO2 bits
(CR1.3 and CR1.4) in host mode.
Custom transmit pulse shapes may be implement-
ed by writing pulse shape coefficients to the regis-
ters. Custom pulses may be used to correct for
pulse shape degradation or distortion caused by
improper termination, suboptimal interconnect wir-
ing, or loading from external components such as
high voltage protection devices.
For DS-1 applications, the arrangement in Table 1
meets ANSI T1.102 pulse shape requirements. A
DS440F1 FEB ‘03
Interface Modes
Master Clocks
Transmitter
typical output pulse is shown in Figure 6. These
pulse settings can also be used to meet ITU-T
pulse shape requirements for 1.544 MHz opera-
tion.
Setting TNEG high for more than 16 TCLK cycles
enables the coder mode, changing TPOS to TDA-
TA, RPOS to RDATA, and RNEG to BPV. When
configured for coder mode, the MODE pin can be
tied to RCLK enabling the B8ZS encoders and de-
coders.
The CS61310 will detect the absence of TCLK,
and will force TTIP and TRING to high impedance
-0 .5
1 .0
0 .5
0
0
Table 1. Pulse Shape Selection and Transformer
N O R M AL IZE D
AM P L IT U D E
Figure 6. Typical Pulse Shape for DS-1
LBO2
0
0
1
1
2 5 0
P U L SE S H A PE
LBO1
O U T P U T
T IM E (n a n o se co n d s)
Requirements
0
1
0
1
5 00
Output Pulse
-22.5 dB
-7.5 dB
-15 dB
0 dB
S P E C IFIC A T IO N
A N S I T I.1 0 2
7 5 0
CS61310
1 00 0
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