DS3251/DS3252/DS3253/DS3254
2. DETAILED DESCRIPTION
The DS3251 (single), DS3252 (dual), DS3253 (triple), and DS3254 (quad) LIUs perform the functions necessary
for interfacing at the physical layer to DS3, E3, or STS-1 lines. Each LIU has independent receive and transmit
paths and a built-in jitter attenuator. The receiver performs clock and data recovery from a B3ZS- or HDB3-coded
alternate mark inversion (AMI) signal and monitors for loss of the incoming signal. The receiver optionally performs
B3ZS/HDB3 decoding and outputs the recovered data in either binary or bipolar format. The transmitter accepts
data in either binary or bipolar format, optionally performs B3ZS/HDB3 encoding, and drives standard pulse-shape
waveforms onto 75ꢀ coaxial cable. The jitter attenuator can be mapped into the receiver data path, mapped into
the transmitter data path, or be disabled. An on-chip clock adapter generates all line-rate clocks from a single input
clock. Control interface options include 8-bit parallel, SPITM, and hardware mode. The DS325x LIUs conform to the
telecommunications standards listed in Table 1-A. Figure 2-1 shows the external components required for proper
operation.
Shorthand Notations. The notation “DS325x” throughout this data sheet refers to either the DS3251, DS3252,
DS3253, or DS3254. This data sheet is the specification for all four devices. The LIUs on the DS325x devices are
identical. For brevity, this document uses the pin name and register name shorthand “NAMEn,” where “n” stands in
place of the LIU port number. For example, on the DS3254 quad LIU, TCLKn is shorthand notation for pins TCLK1,
TCLK2, TCLK3, and TCLK4 on LIU ports 1, 2, 3, and 4, respectively. This document also uses generic pin and
register names such as TCLK (without a number suffix) when describing LIU operation. When working with a
specific LIU on the DS325x devices, generic names like TCLK should be converted to actual pin names, such as
TCLK1.
Figure 2-1. External Connections
TRANSMIT
EACH LIU
TXP
VDD
0.1ꢀF
0.1ꢀF
0.01ꢀF
0.01ꢀF
1ꢀF
1ꢀF
3.3V
POWER
PLANE
330ꢁ
VDD
(1%)
0.05ꢀF
(optional)
VDD
TXN
0.1ꢀF
0.01ꢀF
1ꢀF
1:2ct
Dallas
Semiconductor
RECEIVE
DS325x
VSS
RXP
GROUND
PLANE
330ꢁ
VSS
VSS
(1%)
0.05ꢀF
(optional)
RXN
1:2ct
3. APPLICATION EXAMPLE
Figure 3-1. 4-Port Unchannelized DS3/E3 Card
DS3254
QUAD
DS3144
QUAD
DS3/E3/STS-1
LIU
DS3/E3
FRAMER
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