STANDARD PRODUCT
PM4351 COMET
DATA SHEET
PMC-1970624
ISSUE 10
COMBINED E1/T1 TRANSCEIVER
frequencies above 20 kHz. When ALGSEL is set to logic 0, the jitter
tolerance is increased for frequencies below 20 kHz (i.e. the tolerance is
improved by 20% over that of ALGSEL=1 at these frequencies), but the
tolerance approaches 0.4 UIpp at the higher frequencies.
AMI:
The alternate mark inversion (AMI) bit specifies the line coding of the
incoming signal. A logic 1 selects AMI line coding by disabling HDB3
decoding if E1 mode and B8ZS in T1 mode. In E1 mode, a logic 0 selects
HDB3 line decoding which entails substituting an HDB3 signature with four
zeros. In T1 mode, a logic 0 selects B8ZS line decoding which entails
substituting an B8ZS signature with eight zeros.
LOS[1:0]:
The loss of signal threshold is set by the operating mode and the state of the
AMI, LOS[1] and LOS[0] bits:
Table 20
- Loss of Signal Thresholds
Mode AMI LOS[1] LOS[0] Threshold (PCM periods)
E1
T1
X
0
0
0
0
0
0
1
1
0
0
0
1
0
1
10
15
15
31
63
175
1
X
X
X
X
X
X
When the number of consecutive zeros on the incoming PCM line exceeds
the programmed threshold, the LOSV status bit is set. For example, if the
threshold is set to 10, the 11th zero causes the LOSV bit to be set. The LOSV
bit clears when a pulse occurs.
PROPRIETARY AND CONFIDENTIAL
109
PMC [ PMC-SIERRA, INC ]
