Released
Datasheet
PM73487 QRT
PMC-Sierra, Inc.
PMC-980618
Issue 3
622 Mbps ATM Traffic Management Device
2.2.9 SE_SOC Encodings
The SE_SOC and BP_ACK signals have guaranteed transitions and special encodings, which are
defined in this section and in “BP_ACK Encodings” which follows. The SE_SOC_IN and
SE_SOC_OUT signals have guaranteed transitions and SOC encodings as shown in Figure 15.
The SE_SOC signals carry a repeating pattern of four zeros and four ones to guarantee transitions
required by the phase aligner. The “Start-Of-Cell” on the data lines associated with an SE_SOC
line is indicated by a change in this pattern. For a valid SE_SOC, the change in pattern is followed
by reset of the background pattern such that it is followed by four zeros and four ones. The first
nibble (PRES) of the header is coincident with SE_SOC (change in pattern).
SE_CLK
SE_SOC_OUT
4 ones. 4 zeros
4 ones
4 zeros
4 ones 4 zeros.
4 ones
4 zeros.
5 zeros
4 ones
4 zeros.
Tsesu
Tseho
Tsesu
Magnified CLK
Magnified Data
PRES.
Magnified SE_SOC_OUT
4 ones
4 zeros
1 one.
5 zeros
Figure 15. SE_SOC Encodings
2.2.10 BP_ACK Encodings
Figure 16 shows the BP_ACK encodings.
Mode
Data1
Data0
Inversion1 Data2
Inversion2 Code Ext 0
clk
BP_ACK Base Pattern
BP_ACK Signaling
4 ones
4 zeros
4 ones
4 zeros
Figure 16. BP_ACK Encodings
The BP_ACK_IN and BP_ACK_OUT signals have guaranteed transitions, and BP and ACK
encodings. The BP_ACK signal is used to signal backpressure/cell acknowledgment to the fabric
(QSE) at the egress and receive backpressure/cell acknowledgment at the ingress from the fabric
(QSE).
To ensure the transitions required by the phase aligner, the BP_ACK signal carries a repeating
four zeros, four ones pattern. The actual information is transferred through encoded 7-bit packets
that start with a change in this background pattern. The change (an inversion) on the line is fol-
lowed by a mode bit, followed by two bits of coded message, and a second inversion (inverse of
the first inversion). If it is an acknowledgment packet, this is followed by two bits of code exten-
16
PMC [ PMC-SIERRA, INC ]
