CS61880 datasheet(24/70 Pages) CIRRUS

24 / 70 page

CS61880

DS450PP3

9. TRANSMITTER

The CS61880 contains eight identical transmitters

that each use a low power matched impedance driv-

er to eliminate the need for external load matching

resistors, while providing superior return loss. As a

result, the TTIP/TRING outputs can be connected

directly to the transformer allowing one hardware

circuit for E1 120

Ω, and E1 75 Ω applications.

Digital transmit data and clock are input into the

CS61880 through the TPOS/TDATA, TNEG and

TCLK input pins. These pins accept data in one of

three formats: unipolar, bipolar, or RZ. In either

unipolar or bipolar mode, the CS61880 internally

generates a pulse shape compliant to the G.703

mask for E1 (Refer to Figure 6). The pulse shaping

applied to the transmit data can be selected in hard-

ware mode or in host mode.

In hardware mode, the line impedance (75

Ω or

120

Ω) and which prestored pulse shape to transmit

(75

Ω or 120 Ω) is selected via the CBLSEL pin for

all eight transmitters.

In host mode, each channel is configured indepen-

dently by writing to the Line Length Channel ID

then writing the desired line length settings to the

LEN[3:0] bits in the Line Length Data Register

(11h) (See Section 14.18 on page 38). The LEN

bits select the pulse shape and line impedance of

the addressed channel. In host mode, the CBLSEL

pin is not used.

NOTE: If one channel is configured for E1 75

Ω mode,

another channel can be configured for E1

120

Ω mode at the same time. This operation is

only allowed in host mode.

The CS61880 also allows the user to customize the

transmit pulse shapes to compensate for non-stan-

dard cables, transformers, or protection circuitry.

For further information on the AWG Refer to Ar-

bitrary Waveform Generator (See Section 15 on

page 42).

For more information on the host mode registers re-

fer to Register Descriptions (See Section 14 on

page 35).

9.1 Bipolar Mode

Bipolar mode provides transparent operation for

applications in which the line coding function is

performed by an external framing device. In this

mode, the falling edge of TCLK samples NRZ data

on TPOS/TNEG for transmission on TTIP/TRING.

9.2 Unipolar Mode

In unipolar mode, the CS61880 is configured such

that transmit data is encoded using HDB3, or AMI

line codes. This mode is activated by holding

269 ns

244 ns

194 ns

219 ns

488 ns

Nominal Pulse

100

110

120

-10

-20

Percent of

nominal peak

voltage

Figure 6. Pulse Mask at E1 Interface

CS61880 датащи(PDF) 24 Page - Cirrus Logic

CS61880 датащи(HTML) 24 Page - Cirrus Logic

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70

датащи скачать

ссылки URL