Ambassador T8100A, T8102, and T8105
H.100/H.110 Interfaces and Time-Slot Interchangers
Advance Data Sheet
November 1999
2 Architecture and Functional Descrip-
tion (continued)
H.100 BUS
OUTPUT
CONNECTIONS
2.4 Subrate Switching for the Ambassador
Family (continued)
2.4.5 Limitations
H-BUS TSI
(INCLUDING SUBRATE)
While the structure described above is a relatively sim-
ple extension to the existing architecture, it also
imposes one limitation which must be overcome by
application. To prevent changes in the CAM size and
operation, the assumption is that the data is utilized
only once after the stream plus time slot has been rec-
ognized. (This prevents the multiple hit/multiple access
scenario, in which a byte which contains multiple sub-
rate pieces will not have to be accessed several times.)
To gain access to all subrate pieces present in one
incoming byte, that same byte must be broadcast on
multiple stream plus time slots. In this case, each sub-
rate piece can be switched to the appropriate output.
The ideal scenario is to make use of local switching
(either the local TSI or the local CAM) to provide a
loopback for broadcasting the byte in question. Specifi-
cally, the byte is switched to multiple time slots on a
local output. (The packed byte is coming either from a
local input or from the H.100 bus.) The local output is
physically tied to a free local input, and, in turn, the
multiple time slots are subrate switched to the appropri-
ate outputs (on the H.100 bus, for example). This intro-
duces an additional delay of one frame, but allows for
efficient utilization of the H.100 bus as a subrate
switching fabric (see Figure 14).
LOCAL INPUT 0
1 TIME SLOT
LOCAL TSI
LOCAL INPUT 1
4 TIME SLOTS
LOCAL OUT 1
4 TIME SLOTS
(OR LOCAL-LOCAL
VIA LOCAL CAM)
LOOPBACK WIRE
5-7148F
H.100 BUS
OUTPUT
CONNECTIONS
INPUT
1 TIME SLOT
H-BUS TSI
(INCLUDING SUBRATE)
LOCAL TSI
LOCAL INPUT 1
4 TIME SLOTS
LOCAL OUT 1
4 TIME SLOTS
(OR LOCAL-LOCAL
VIA LOCAL CAM)
LOOPBACK WIRE
5-7149F
INPUT
(LOCAL BROADCAST)
A1 A2 A3 A4
A1 A2 A3 A4 A1 A2 A3 A4 A1 A2 A3 A4 A1 A2 A3 A4
A1
A3
A2
LOCAL OUTPUT-
LOOPBACK INPUT
A4
H-BUS OUTPUTS (EXAMPLE SHOWS SEPARATE STREAMS)
5-7149F
Figure 14. Unpacking Example Using Local
Loopback
42
Lucent Technologies Inc.
AGERE [ AGERE SYSTEMS ]
