PM5364 pmc-sierra, PM5364 Datasheet - Page 233

• Manufacturer Part Number: PM5364
• Description: Tupp 2488 Assp Telecom Standard
• Manufacturer: pmc-sierra

Proprietary and Confidential to PMC-Sierra, Inc., and for its customers’ internal use.
Document No.: PMC-2011334, Issue 7
Figure 60 compares the actual decay of the DC voltage on a link with the value calculated by
the DC balance monitor. The time constant is 10 ms and the input is assumed to have a balanced
number of ones and zeros. The smooth exponential curve is the actual voltage. The
approximation with smaller steps uses a decay factor of 1/8 and a decay period set to 430. The
second approximation uses a decay factor of 1/4 and a decay period of 850. The DC_BAL_EN
bit must be set to logic 1 in addition to setting the CID_TRAN_DC_EN bit to logic 1 for the DC
balance monitor to be enabled.
Figure 61 shows the DC balance count over a few frames times with scrambled random data.
The decay period is set to 430 and the decay factor is 1/8. Simulations have shown that random
data with no bias has maximum DC balance counts of approximately +/-350. With 51% ones
and 49% zeros the maximum DC balance counts are around +/-900. Normal SONET data will
have a ones density between 49.5% and 50.5% a threshold of 1000 is recommended.
Figure 60 DC Balance Decay
TUPP™ 2488 ASSP Telecom Standard Product Data Sheet
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