Bt8370/8375/8376
3.7 Receive LIU Registers
Fully Integrated T1/E1 Framer and Line Interface
OOR_BLOCK
Disable Automatic RLBO—When active, automatic RLBO switching is disabled when the
ADC is out of range.
0 = normal operation
1 = disable RLBO switching
RLB0
Receiver Line Build Out—Enables receive signal attenuation.
0 = RLBO forced off (normal operation)
1 = enable automatic RLBO
LONG_EYE
Eye Open Timeout
0 = 4096 bit timeout
1 = 8192 bit timeout (normal operation)
023—RPLL Low Pass Filter (LPF)
7
6
5
4
3
2
1
0
—
LPF[6]
LPF[5]
LPF[4]
LPF[3]
LPF[2]
LPF[1]
LPF[0]
LPF[6:0]
RPLL Low Pass Filter Gain—Reserved for CONEXANT Production test. Determines clock
recovery RPLL input jitter tolerance and the worst case signal acquisition time. The initial
default value is optimized for maximum input jitter tolerance.
024—Variable Gain Amplifier Maximum (VGA_MAX)
7
6
5
4
3
2
1
0
—
—
VGA_MAX[5]
VGA_MAX[4]
VGA_MAX[3]
VGA_MAX[2]
VGA_MAX[1]
VGA_MAX[0]
VGA_MAX[5:0]
VGA Maximum—The processor can limit receiver sensitivity by programming the maximum
allowable input signal gain into the VGA_MAX register. This option is used for short and
medium haul interfaces that must declare loss of signal when the receive level falls below a
certain level. The default value is 0x3F for Bt8370 and 0x2F for Bt8375/6.
Table 3-10 contains approximate VGA_MAX settings for the receive sensitivity values. The
sensitivity value is the received signal level (below nominal) at which analog loss of signal
(RALOS) occurs. These values are applicable only when the RLBO and the PRE_EQ are
disabled. RLBO is disabled when the receive level is less than about –8 dB, or when RLBO is
forced off: RLBO = 0 (reg RLIU_CR [add 022]. The PRE_EQ is disabled when the receive
level is greater than about –24 dB, or when it is forced off: register PRE_EQ [addr 02A] =
(10XXXXXX).
Table 3-10. VGA Maximum Settings for Receive Sensitivity
Rx Sensitivity
VGA_MAX
0 dB
–5 dB
–10 dB
–15 dB
–20 dB
–25 dB
–30 dB
–35 dB
–40 dB
–45 dB
0x0B
0x12
0x19
0x1E
0x23
0x27
0x2C
0x2F
0x33
0x37
3-42
Conexant
N8370DSE
CONEXANT [ CONEXANT SYSTEMS, INC ]
