CS61581 datasheet(11/37 Pages) CIRRUS

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CS61581

DS211PP8

loading from external components such as high

voltage protection devices.

For T1 DSX-1 applications, line lengths from 0 to

655 feet (as measured from the transmitter to the

DSX-1 cross connect) may be selected. The five

partition arrangement in Table 1 meets ANSI

T1.102 pulse shape requirements when using #22

ABAM or AT&T 600 series cable. A typical output

pulse is shown in Figure 6. These pulse settings can

also be used to meet ITU-T pulse shape require-

ments for 1.544 MHz operation. Short haul pulse

shapes for T1 and E1 are selected by the LEN[2:0]

bits in Control Register 1.

Note that when the device is operated at E1 fre-

quency in the hardware mode, it defaults to low im-

pedance, long haul mode. The pulses driven by the

transmitter in this mode are T1.403 (350ns) pulses

with an overshoot and an undershoot. To drive

pulses without overshoot and undershoot in E1

long haul mode, the E1_LH bit (CR3.6) must be set

to 1, with the SH/LH bit (CR2.0) set to 0.

The E1 G.703 pulse shape is supported with line

length selections LEN[2:0] = 000 for 2.37 V 75

applications or LEN[2:0] = 001 for 3.0 V 120

. ap-

plications. The output pulse will meet the G.703

pulse shape template shown in Figure 7. The output

impedance of the driver will adjust according to the

pulse shape selected.

In the short haul mode, setting the LEN[2:0] bits

also controls the transmitter output impedance. For

long haul operation, driver impedance is deter-

mined by the desired selection of MATCHZ and

E1_LH bits. When MATCHZ is set to “0” the out-

put impedance is low, and the impedance presented

to the line is controlled by external resistors. When

MATCHZ is set to 1, E1_LH determines whether

* MATCHZ = CR2.5

Long Haul

LB02

LB01

Output Pulse

0 dB

-7.5 dB

-15 dB

-22.5 dB

Transformer Turns

Ratio

Mode

Transmit Receive

HDW or MATCHZ* = 0

1:2

1:1

MATCHZ* = 1

1:1.5

1:1

Short Haul

LEN2

LEN1

LEN0

Output Pulse

Line Z

2.37 V

3.0 V

120

011

DSX-1

0’-133’

100

DSX-1

133’-266’

100

101

DSX-1

266’-399’

100

110

DSX-1

399’-533’

100

111

DSX-1

533’-655’

100

ANSI

T1.403

100

010

FCC Part 68,

Option A

6.0 V

100

Table 1. Pulse Shape Selection and Transformer Requirements

CS61581

DS211F1

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