PM9313 datasheet(76/343 Pages) PMC

76 / 343 page

PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE

PM9311/2/3/5 ETT1™ CHIP SET

PMC-2000164

ISSUE 3

ENHANCED TT1™ SWITCH FABRIC

Released

Data Sheet

PMC-Sierra, Inc.

Start/Stop Control Packets

Start/Stop Control Packets are used to toggle the flow of data traffic over the link (here, data traffic is

defined to be TDM, best-effort unicast and multicast segment payloads and associated requests and

grants. i.e. all non-Control Packet segments). Start/Stop Control Packets can be sent over an LCS link in

either direction.

If a linecard sends a Stop Control Packet to the switch core, the switch core will stop sending grants to the

linecard for ingress data traffic, and will stop sending egress data traffic to the linecard. When a Start

Control Packet is sent, grants and egress data traffic resume.

If the switch core sends a Stop Control Packet to a linecard, the linecard must stop sending new data traffic

requests into the switch core until a Start Control Packet is sent.

Note that when either end has received a Stop Control Packet, it can continue to request, grant, send and

receive all categories of Control Packets.

When an LCS link powers-up, it will be in Stop mode: i.e. it will act as if a Stop Control Packet has been

sent in both directions.

1.6.3.2

CPU Control Packets

CPU Control Packets are specified by setting the Label_1/Label_2 Field to 14’h0001 (CP-category for

CPU Control Packets) and associated Type Field to 4’h0 (Type for Control Packets).

When the linecard sends a CPU CP to the switch core CPU, the complete payload data is passed to the

switch core CPU. Likewise, when the switch core sends a CPU CP to the linecard, the complete payload

data is passed to the linecard.

No flow control mechanism is explicitly implemented for CPU CPs, and will be implementation dependent.

Table 14.

Start/Stop Control Packet Format

Field

Size

(bits)

Definition

CP_Type

00000010

Start/Stop

1=Start, 0=Stop.

Unused

Set to zero.

CRC-16

16-bit CRC calculated over 10-byte control packet payload.

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