BT8376EPF datasheet(182/323 Pages) CONEXANT

182 / 323 page

Bt8370/8375/8376

3.11 Transmit LIU Registers

Fully Integrated T1/E1 Framer and Line Interface

3-64

Conexant

N8370DSE

3.11 Transmit LIU Registers

Unused bits indicated by a dash (—) are reserved and should be written to 0. Writing to reserved bits has no

effect.

060–067—Transmit Pulse Shape Configuration (SHAPE)

SHAPE[5:0]

Initialized to default values when the processor writes to addr 068. Refer to pulse shape

description in Transmit LIU section (Figure 2-39, Digitized AMI Pulse Shape).

068—Transmit LIU Configuration (TLIU_CR)

After writing to TLIU_CR, the processor should wait for eight MCLK-cycles before reading back TLIU_CR.

This is because any write into TLIU_CR triggers an internal transfer of ROM data to update the SHAPE

registers. While this internal transfer is in progress, any read or write of TLIU_CR may be blocked internally or

it will return an incorrect read value.

TURNS

Transmit Transformer Turns Ratio—Transmit DAC automatically scales the XTIP/XRING

outputs for the selected transformer turns ratio. The transmit DAC is current-limited and

cannot source sufficient current to drive full-height output pulses when an external transmit

termination resistor and 1:1.15 transformer is selected.

0 = 1:1.36 transformer

1 = 1:1.15 transformer (reduced amplitude if TERM also enabled)

TERM

Transmit Termination Resistor—Transmit DAC automatically scales the XTIP/XRING output

amplitude to compensate for the presence of an optional external termination resistor. The

external resistor (51.1

Ω) is placed in parallel across XTIP/XRING on systems that must meet

–18 dB transmitter return loss requirements. Better return loss is also possible by more closely

matching transmitter and cable impedances, at the expense of higher power dissipation and

lower output signal amplitude. (Refer to Figure 2-45, External Termination Resistor

Placement for resistor placement. Refer to Table 3-14, Return Loss Values for return loss

values.)

0 = internal transmit impedance (14.0 k

Ω)

1 = external transmit termination

——

SHAPE[5]

SHAPE[4]

SHAPE[3]

SHAPE[2]

SHAPE[1]

SHAPE[0]

TURNS

TERM

LBO[1]

LBO[0]

PULSE[2]

PULSE[1]

PULSE[0]

AISCLK

BT8376EPF Datasheet(PDF) 182 Page - Synaptics Incorporated.

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