Agere Systems Inc.
151
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)
14.2.2.3.2 Subrate Switching Using T8110
The H1x0 bus and the local stream bus are based on byte-oriented TDM data streams—data is always switched
as whole bytes. The subrate data must be packed into these bytes prior to switching (refer to Sections 14.2.2.3.3
and 14.2.2.3.4). The data bytes are not necessarily constrained to using fully packed bytes—any portion of a byte
may be used. Subrate switching using T8110 requires the following:
n
Overall subrate enable mode is activated (register 0x00105, data memory mode select bit 7 is set; see Section
6.1.3 on page 48).
n
The subrate field of the connection memory entry for that switch connection is set up. This field contains 7 bits
which control the type of subrate (i.e., bit, di-bit, nibble, or byte), and the data bit shuffling within the TDM byte
data,
from
and
to
(refer to Figure 36 on page 137, Figure 43 on page 141, and Table 114).
n
The VFC connection memory bit for cases where a double-buffering configuration is set up in the data memory
(refer to Figure 36, Figure 43, and Sections 14.2.1.2, 14.2.2.1).
In order to program a subrate simplex connection, the subrate field is only required for the
from
half of that con-
nection. Incoming serial byte data has its bit positions rearranged based on the subrate field contents prior to being
written into the data memory. For double-buffered data memory configurations, the VCF bit controls which of two
data pages the rearranged byte is written to. The
to
half of a subrate simplex connection simply outputs the entire
byte found at the data memory location used for that connection, and its connection memory subrate field is
ignored.
Table 113. Subrate Switching, Data Propagation Rate vs. Channel Capacity
Subrate Type
Bits per Channel
Channel Data Propagation Rate
(Bits/Frame x 8K Frames/s)
8 Kbits/s
16 Kbits/s
32 Kbits/s
64 Kbits/s
Channel Capacity
(Relative to Byte Switching)
8X
4X
2X
1X
Bit
Di-bit
Nibble
1
2
4
8
Byte (no subrate)
Table 114. Subrate Switching, Connection Memory Programming Setup
Subrate
Type
Bit
Subrate Connection Memory Bit Field (6:0)
4
3
000 =
from
bit 0
001 =
from
bit 1
010 =
from
bit 2
011 =
from
bit 3
100 =
from
bit 4
101 =
from
bit 5
110 =
from
bit 6
111 =
from
bit 7
Subrate Connection Memory Bit Field (6:0)
4
3
00 =
from
bits[1:0]
01 =
from
bits[3:2]
10 =
from
bits [5:4]
11 =
from
bits[7:6]
6
1
5
2
1
0
000 =
to
bit 0
001 =
to
bit 1
010 =
to
bit 2
011 =
to
bit 3
100 =
to
bit 4
101 =
to
bit 5
110 =
to
bit 6
111 =
to
bit 7
6
5
2
1
0
Di-Bit
01
Reserved
00 =
to
bits[1:0]
01 =
to
bits[3:2]
10 =
to
bits[5:4]
11 =
to
bits[7:6]