Bt8370/8375/8376
3.11 Transmit LIU Registers
Fully Integrated T1/E1 Framer and Line Interface
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)
7
6
5
4
3
2
1
0
—
—
SHAPE[5]
SHAPE[4]
SHAPE[3]
SHAPE[2]
SHAPE[1]
SHAPE[0]
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.
7
6
5
4
3
2
1
0
TURNS
TERM
LBO[1]
LBO[0]
PULSE[2]
PULSE[1]
PULSE[0]
AISCLK
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
3-64
Conexant
N8370DSE
CONEXANT [ CONEXANT SYSTEMS, INC ]
