152
Agere Systems Inc.
Data Sheet
May 2001
and Packet Payload Engine
Ambassador T8110 PCI-Based H.100/H.110 Switch
14
Connection Control—Standard and Virtual Channel
(continued)
14.2.2.3.3 Subrate Packing of Outgoing Bytes
The output from subrate connections is always an entire byte so that it does not violate the H.100 or H.110 specifi-
cations. The output byte is composed of smaller, i.e., subrate pieces. The process of combining the incoming
pieces into a whole byte suitable for output is called
packing
. In the T8110 (and other subrate-capable Ambassa-
dordevices),
packing
is accomplished by making several
from
connections for each single
to
connection. For
example, in Figure 48, four
from
connections (of different stream/time-slot origins), all di-bits, are used to construct
a byte that will be output as defined by the
to
connection.
The outgoing
to
half of a simplex connection reads an entire byte from a data memory location. The packing of
separate incoming subrate pieces into this byte is achieved by setting up multiple
from
one-half simplex connec-
tions for one
to
one-half simplex connection, all using the same data memory location. An example is illustrated in
Figure 48. This example shows the packing of four separate incoming di-bits from four different channels into one
outgoing byte on one channel.
Note:
Please note the limitation that multiple di-bits from the same time slot cannot be switched simultaneously.
This would require the byte of that time slot to be unpacked first, which is discussed in Section 14.2.2.3.4 on
page 153.
Subrate
Type
Nibble
Subrate Connection Memory Bit Field (6:0)
4
3
0 =
from
bits[3:0]
1 =
from
bits[7:4]
Subrate Connection Memory Bit Field (6:0)
4
3
6
5
001
2
1
0
Reserved
0 =
to
bits[3:0]
1 =
to
bits[7:4]
6
5
000
2
1
0
Byte
Reserved
Table 114. Subrate Switching, Connection Memory Programming Setup
(continued)