BT8376EPF datasheet(157/323 Pages) CONEXANT

157 / 323 page

Bt8370/8375/8376

Fully Integrated T1/E1 Framer and Line Interface

3.7 Receive LIU Registers

N8370DSE

Conexant

3-39

020—LIU Configuration (LIU_CR)

NOTE:

Bits 0 and 1 are reserved and should be written to the values shown.

RST_LIU

Reset RLIU—Writing a 1 to RST_LIU resets the RLIU, reinitializes the receive equalizer, and

re-attempts signal acquisition. The processor must reset the RLIU after changing ATTN, or

after changing equalizer coefficients [EQ_DAT; addr 025]. Optionally, it can be reset in

response to an extended alarm condition.

0 = normal

1 = reset RLIU (self clears)

SQUELCH

Enable Squelch—Data slicer outputs from RLIU are forced to 0 until EYEOPEN [addr 021] =

1. SQUELCH is useful for long haul applications when near-end crosstalk may be of sufficient

magnitude to prevent accurate loss of signal detection.

0 = no effect

1 = squelch data slicer output

FORCE_VGA

FORCE VGA—Internal Variable Gain Amplifier (VGA) is set to equal the value programmed

in VGA_MAX register (addr 024). This bit is used for test purposes only.

0 = normal operation

1 = force VGA to VGA_MAX (test mode only)

RDIGI

Enable Receive Digital Inputs—When set, RDIGI bypasses RLIU and enables

RPOSI/RNEGI/RCKI inputs provided by an external line interface; otherwise, bipolar

RTIP/RRING inputs are enabled, RCKI input is ignored, and RPLL recovers the received

clock.

0 = RTIP/RRING inputs enabled

1 = RPOSI/RNEGI/RCKI inputs enabled

ATTN[1:0]

Bridge Attenuation—The receive equalizer can automatically compensate for signal level

attenuation caused by placement of bridge resistors in series with the normal receive

termination resistance. Bridge compensation scales the equalizer coefficients because they are

loaded from internal ROM; therefore, any change to the ATTN setting must be followed by an

RLIU reset command (RST_LIU).

RST_LIU

SQUELCH

FORCE_VGA

RDIGI

ATTN[1]

ATTN[0]

ATTN

Bridge Attenuation

Bridge Resistance

0 dB

None

–10 dB

300

Ω

–20 dB

1000

Ω

–30 dB

1500

Ω

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