CS61581 데이터 시트보기 (PDF) - Cirrus Logic

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CS61581

T1/E1 Universal Line Interface

Cirrus Logic 

CS61581

NORMALIZED

AMPLITUDE

1.0

0.5

ANSI TI.102,

AT&T CB 119

SPECIFICATIONS

0

-0.5

0

OUTPUT

PULSE SHAPE

250

500

750

TIME (nanoseconds)

1000

Figure 6. Typical Pulse Shape at DSX-1 Cross Connect

the driver is set for 100Ω (E1_LH = 0) or 120Ω

(E1_LH = 1).

The CS61581 will detect the absence of TCLK, and

will force TTIP and TRING to high impedance af-

ter 175 bit periods, preventing transmission when

data input is not present. In host mode, the trans-

mitter can be set to high impedance by setting the

TxHIZ bit, CR2.1, to “1.”

When any transmit control bit (TAOS, LEN0-2,

LBO1-2, or LLOOP) is toggled, the transmitter

outputs will require approximately 22 bit periods to

stabilize. The transmitter will take longer to stabi-

lize when RLOOP is selected because the timing

circuitry must adjust to the new frequency.

The CS61581 has the option to drive a 6 Vpeak

pulse. The option is used for driving external equal-

izers used in T1 DSX applications that conform to

FCC Part 68, Option A. This configuration is se-

lected by setting the LEN[2:0] control bits in regis-

ter 0x10 to 010 in the short haul configuration. The

Percent of

nominal

peak

voltage

120

110

100

90

80

269 ns

244 ns

194 ns

50

10

Nominal Pulse

0

-10

-20

219 ns

488 ns

Figure 7. Mask of the Pulse at the 2048 kbps Interface

turns ratio of the transmit transformer must be set

accordingly: in Matched Impedance mode, the

turns ratio must be 1:1.5; in Low Impedance mode,

the transformer turns ratio = 1:2.6.

2.4 Transmit All Ones Select

The transmitter provides for all ones insertion at the

frequency of TCLK. If TCLK is absent, then

MCLK is used (or the quartz crystal generated fre-

quency in the absence of MCLK). Transmit all

ones is selected when TAOS (pin 28 in hardware

mode, CR1.7 in host mode) goes high, and causes

continuous ones to be transmitted on the line (TTIP

and TRING). When TAOS is active, the TPOS and

TNEG (TDATA) inputs are ignored. If Remote

Loopback is in effect, any TAOS request will be ig-

nored.

12

DS211PP8

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