PM5364 pmc-sierra, PM5364 Datasheet - Page 235

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

13.15.3
13.16 Bypasses
13.16.1
13.16.2
13.16.3
Proprietary and Confidential to PMC-Sierra, Inc., and for its customers’ internal use.
Document No.: PMC-2011334, Issue 7
Normal SONET data has a ones density between 49.5% and 50.5% over a large data sample.
Simulations with random data having a ones density of 55% have shown that the minimum
number of transitions in 255 bytes is 898 (44.0%). To configure the transition detector the
transition threshold must be set to one of the values enumerated in Table 45. The suggested
setting for both 622 Mbit/s and 2.488 Gbit/s links is 7.
Table 45 Transition Thresholds
TRAN_THRESH[2:0]
0
1
2
3
4
5
6
7
There are a number of bypasses available in the TUPP 2488 used for device debug. Some
bypasses are also required for normal applications to work correctly.
MSU-Lite Bypasses
Each bank of MSUs can be bypassed separately. The top level registers to do this are
IMSU_BYPASS and EMSU _BYPASS. These bypass the entire STS-48 (4 MSUs) since
bypassing the MSUs individually will cause latency mismatches between different OC-12s.
Bypassing MSU has the exact effect of sending column 1 input to column 1 output etc. (but
avoids the need of setting up configuration RAMs with a 1 to 1 mapping). This should only be
used when debugging the device.
CCB Bypass
CCB can be bypassed by asserting the CCB_BYPASS register. This bypasses the entire STS-
192 worth of information through the CCB. The main use of this feature is described in Figure
45.
ILC Bypasses
The TX_BYPASS and RX_BYPASS in the TILC and RILC respectively bypass the message
transmission and receive capabilities of the ILC blocks. All signals passing through the ILCs are
unaffected.
Transition Detector
Threshold
disabled
128
256
384
512
640
768
896
Transition Density
disabled
6.3%
12.5%
18.8%
25.1%
31.4%
37.6%
43.9%
TUPP™ 2488 ASSP Telecom Standard Product Data Sheet
Released
235