MT90520 Datasheet, PDF (174/180 Pages) Zarlink Semiconductor Inc – 8-Port Primary Rate Circuit Emulation AAL1 SAR

MT90520
Data Sheet
Mode
Total Static TX /
Segmentation
(µsec)
Total Static RX /
Reassembly
(µsec)
End-to-End Latency
(µsec)
UDT T1 - min 245.8
1.7 + 2.59 X Max_Lead
490.96 + CDV + network
max 245.8
245.2 + 2.59 X Max_Lead
734.46 + CDV + network
UDT E1 - min 185.9
1.7 + 1.95 X Max_Lead
370.9 + CDV + network
max 185.9
185.3 + 1.95 X Max_Lead
554.5 + CDV + network
SDT - min 125 + FLOOR[46/N] X 125 125 + 62.5 X Max_Lead
375 + FLOOR[46/N] X
125 + CDV + network
max 125 + CEIL[47/N] X 125 250 + 62.5 X Max_Lead
500 + CEIL[47/N] X 125
+ CDV + network
SDT Trunking - min 250
125 + 62.5 X Max_Lead
500 + CDV + network
max 250
250 + 62.5 X Max_Lead
Table 107 - End-to-End Latency
625 + CDV + network
Since the variable portions of the delay in segmentation and reassembly effectively become part of the CDV that
must be compensated for in the CDV buffer, we can omit them from the end-to-end calculation. (Also remembering
that the variable delays given in Table 105 and Table 106 are worst-case numbers that will never be experienced by
most applications.) The delay variation in SDT mode due to payload size variation and divide-by-N remainders is
also part of the CDV compensated for by the CDV buffer, but is left in here to illustrate the effects on delay of the
value of N.
The Max_Lead values should be set by the user in accordance with the expected or negotiated CDV, as explained
in “UDT Mode of Operation” on page 78 and in “SDT Mode of Operation” on page 79. These recommended settings
are used to evaluate Max_Lead in Table 107. It can be seen that the difference between the minimum and
maximum static delay in each mode is due largely to the pointer offset, which, as described earlier, is the random
offset between the time of the segmentation operation and the time of the reassembly operation.
The delay values for SDT assume no TDM switching delay. This means that the given delay is for a TDM byte
which is driven out at the RX end on the same TDM channel number as it was sampled in at the TX end. For
example, if the TDM byte comes into the segmentation end on TDM channel 3, it is driven out at the reassembly
end on TDM channel 3.
174
Zarlink Semiconductor Inc.