S/UNI-IMA-4 Telecom Standard Product Data Sheet
Released
Links containing a T1 or an E1 stream may be channelized. For channelized links, the link clock
is only active during time-slots 1 to 24 of a T1 stream; it is inactive during the frame bit.
Similarly, the clock is only active during time-slots 1 to 31 of an E1 stream and inactive during
the framing bytes. Each time-slot may be independently configured to be provisioned (contain
valid data) or unprovisioned. The RCAS performs a table lookup to assign the provisioned time-
slots to a virtual link. After the selected timeslots are grouped into a virtual link, virtual links
are referred to as links. This look-up should be used to remove byte 16 of the E1 frame, since
byte 16 contains signaling data not ATM data and is also used to implement a fractional T1 or
E1. The first bit of time-slot 1 of a channelized link is identified by noting the absence of the
clock and its re-activation.
Links may also be unchannelized. In this mode, all data is assumed to be valid ATM data. The
link clock is only active during bit times containing data to be processed and inactive during bits
that are to be ignored by the RCAS, such as framing and overhead bits.
The RCAS provides diagnostic line-side loopback that is selectable on a per-channel basis.
When a channel is in diagnostic loopback, data on the received links originally destined for that
channel is ignored. Transmit data of that channel is substituted in its place.
Proprietary and Confidential to PMC-Sierra, Inc., and for its customers’ internal use.
Document No.: PMC-2020889, Issue 2
85
PMC [ PMC-SIERRA, INC ]
