Released
PMC-Sierra, Inc.
PM9311/2/3/5 ETT1™ CHIP SET
Data Sheet
PMC-2000164
ISSUE 3
ENHANCED TT1™ SWITCH FABRIC
portion of a segment called a frame. An LCS linecard or switch should therefore state the number of
channels in a gang and the bytes per channel utilized for its particular implementation.
In the receive direction each channel receives a serial stream of 8B/10B coded data which can be decoded
into a parallel byte stream plus two additional bits - one to indicate a control code-point and one for an
errored code-point. In the transmit direction, an eight bit byte of parallel data plus one bit to indicate control
word is sent through each channel as serialized 8B/10B encoded data.
The optional parallel interface has separate ingress and egress 10-bit parallel buses. The busses operate
in source synchronous mode and so carry a clock with them to latch the data. A source synchronous
transmit clock is driven from the LCS device interface to the Serdes devices. For data arriving from the
remote LCS device, each Serdes device recovers the receive clock from the bit stream and provides it to
the local LCS device’s parallel bus receiver interface.
Table 15 shows the different external interface configurations supported by the ETT1. When utilizing the
parallel interface, a Serdes device is used to convert between the byte-stream and the 8B/10B encoded
serial stream. This Serdes will be a Single Data Rate (SDR) interface for the 1.5 Gbit/s interface.
Table 15. Fiber 1.5 Gbit/s per Channel Interface Configurations
Gang of
Channels
Data Frame
Size
Segment
Size
Segment
Time
Segments
per second
Channel
Data Rate
Channel
Line Rate
12
14
6
6
72
84
40 ns
40 ns
25 M
25 M
1.50 Gbits/s
1.50 Gbits/s
1.5 SDR
1.5 SDR
Table 16. Mapping Segments to 1.5 Gbit/s Channels
Gang
of
Chnls
Data
Frame
Size
Channel
1
Channel
2
Channel
3
Channel
4
Channel
8
Channel
9
Channel
12
Channel
14
Channel
15
14
12
6
Prepend
0-5
Prepend
6-7,
Pyld 0-3
Payload
4-9
Payload
10-15
Payload
34-39
Payload
40-45
Payload
58-63
Payload
70-75
6
Prepend
0-5
Prepend
6-7,
Payload
4-9
Payload
10-15
Payload
34-39
Payload
40-45
Payload
58-63
Pyld 0-3
An LCS segment consists of an eight byte prepend and either a 64- or 76-byte payload. The start of the
prepend is sent on the first channel, any remainder of the prepend is sent on the next channel, followed by
the start of the payload. The remaining channels carry the subsequent bytes of the payload. The exact
mapping of bytes to channels is shown Table 16.
An 8+64 byte segment is not explicitly supported when using the 2.5 Gbaud links. However, any smaller
segment payload than 76 bytes can be supported by padding the fixed length segments to the full 76-byte
payload.
76
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
PMC [ PMC-SIERRA, INC ]
