S/UNI®-ATLAS-3200 Telecom Standard Product Data Sheet
Preliminary
Calendar
Address
4
5
6
7
8
9
10
11
12
13
14
15
Calendar Data
0
1
2
4
0
1
2
5
0
1
2
6
There are two pointers used in the calendar algorithm. They are the polling pointer and the
servicing pointer. The servicing pointer moves down the calendar, and the first positive cell
available assertion the pointer encounters will be the PHY selected for transfer on the next
subsequent opportunity. It is recommended that repeated entries in the calendar be spread in a
uniform manner in the calendar. This will help maximize the chances of selection in a
proportional manner. Information that is gathered during polling is kept and maintained in a
persistent fashion. According to UTOPIA Level 3 specification, once a PHY has asserted cell
available, it is committed to transmission sometime in the future. The servicing algorithm
remembers all assertions for cell available made in the past and advances the servicing pointer
through the responses without regard to the age of the response. This algorithm provides
flexibility in servicing without starvation so long as the number of entries in the calendar for a
PHY is proportional to the bandwidth of that PHY.
Both the polling and servicing algorithms are designed to take into account that Cell Available
signals on connections that are selected are not valid until two cycles after TxL_SOC has been
presented.
Generally, the calendar should be set up at device initialization and subsequently be left
unchanged. When the calendar length, or a calendar entry is updated during cell or packet flow,
there may be an impact on polling, which may result in loss of data for a short period of time on
any PHY that is transferring data.
For maximum efficiency, it is recommended that the RxPhy calendar length be set to at least 64,
and preferably as close to 128 as is practical. A shorter set of calendar entries can simply be
repeated several times to pad out to a greater length.
Proprietary and Confidential to PMC-Sierra, Inc., and for its Customers’ Internal Use
Document ID: PMC-1990553, Issue 4
70
PMC [ PMC-SIERRA, INC ]
