CS61577-IL1Z データシートの表示（PDF） - Cirrus Logic

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CS61577-IL1Z

T1/E1 Line Interface

Cirrus Logic 

CS61577

#3

RTIP

1:2

RRING

Data

Level

Slicer

Edge

Detector

Data

Sampling

& Clock

Extraction

Clock

Phase

Selector

Jitter

Attenuator

RPOS

RNEG

RCLK

Continuously

Calibrated

Delay Line

Figure 10. Receiver Block Diagram

put from the phase selector feeds the clock and

data recovery circuits which generate the recov-

ered clock and sample the incoming signal at

appropriate intervals to recover the data.

Data sampling will continue at the periods se-

lected by the phase selector until an incoming

pulse deviates enough to cause a new phase to be

selected for data sampling. The phases of the de-

lay line are selected and updated to allow as much

as 0.4 UI of jitter from 10 kHz to 100 kHz, with-

out error. The jitter tolerance of the receiver

exceeds that shown in Figure 11. Additionally,

this method of clock and data recovery is tolerant

of long strings of consecutive zeros. The data

300

138

100

28

PEAK-TO-PEAK

JITTER

10

(unit intervals)

Minimum

Performance

AT&T 62411

sampler will continuously sample data based on

its last input until a new pulse arrives to update

the clock phase selector.

The delay line is continuously calibrated using

the crystal oscillator reference clock. The delay

line produces 13 phases for each cycle of the ref-

erence clock. In effect, the 13 phases are

analogous to a 20 MHz clock when the reference

clock is 1.544 MHz. This implementation utilizes

the benefits of a 20 MHz clock for clock recovery

without actually having the clock present to im-

pede analog circuit performance.

In the Hardware Mode, data at RPOS and RNEG

should be sampled on the rising edge of RCLK,

the recovered clock. In the Extended Hardware

Mode, data at RDATA should be sampled on the

falling edge of RCLK. In the Host Mode, CLKE

determines the clock polarity for which output

data should be sampled as shown in Table 5.

1

.4

.1

1

10

100 300 700 1k

10k

100k

JITTER FREQUENCY (Hz)

Figure 11. Minimum Input Jitter Tolerance of Receiver

(Clock Recovery Circuit and Jitter Attenuator)

12

$3DS15050F

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