DS2196 datasheet(119/157 Pages) DALLAS

119 / 157 page

DS2196

119 of 157

Normally, the clock that is output at the RCLKLO pin is the recovered clock from the T1 AMI/B8ZS

waveform presented at the RTIP and RRING inputs. When no AMI signal is present at RTIP and

RRING, a Receive Carrier Loss (LRCL) condition will occur and the RCLKLO will be sourced from the

clock applied at the MCLK pin. If the jitter attenuator is either placed in the transmit path or is disabled,

the RCLKLO output can exhibit slightly shorter high cycles of the clock. This is due to the highly over

sampled digital clock recovery circuitry. If the jitter attenuator is placed in the receive path (as is the case

in most applications), the jitter attenuator restores the RCLK to being close to 50% duty cycle. Please see

the Receive AC Timing Characteristics in Section 22 for more details.

19.2TRANSMIT WAVESHAPING AND LINE DRIVING

The DS2196 uses a set of laser–trimmed delay lines along with a precision Digital–to–Analog Converter

(DAC) to create the waveforms that are transmitted onto the T1 line. The waveforms created by the

DS2196 meet the latest ANSI, AT&T, and ITU specifications. See Figure 19–3. The user will select

which waveform is to be generated by properly programming the LBOS3/LBOS2/LBOS1/LBOS0 bits in

the Line Interface Control Register (LICR).

The DS2196 can set up in a number of various

configurations depending on the application. See Table 19–1 and Figure 19–1.

Table 19-1: LINE BUILD OUT SELECT IN LICR

LBO

LINE BUILD OUT

APPLICATION

0 to 133 feet/

DSX–1/0dB CSU

133 feet to 266

DSX–1

266 feet to 399

DSX–1

399 feet to 533

DSX–1

533 feet to 655

DSX–1

–7.5 dB

CSU

–15 dB

CSU

–22.5 dB

CSU

Square Wave Output

Custom Wave shape

Open Drain Output Driver

Enable

Custom Wave shape

NOTE:

LBOS3 is located at CCR7A.0.

Due to the nature of the design of the transmitter in the DS2196, very little jitter (less then 0.005 UIpp

broadband from 10 Hz to 100 kHz) is added to the jitter present on TCLKLI. Also, the waveforms that

they create are independent of the duty cycle of TCLKLI. The transmitter in the DS2196 couples to the

T1 transmit twisted pair via a 1:2 step up transformer for the as shown in Figure 19–1. In order for the

devices to create the proper waveforms, this transformer used must meet the specifications listed in Table

19–2.

DS2196 Datasheet(PDF) 119 Page - Dallas Semiconductor

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