QR0001 datasheet(21/40 Pages) NSC

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40 Ring Interface (Continued)

TABLE 44 Ring Port Type Field

T 1

T 0

Name

Description

Head

A head symbol appears on Up

or on the Dn Ports

Payload

A data or frame symbol

appears on the Up or on the Dn

Ports

Tail

The last payload symbol of a

packet appears on the Up or Dn

Ports

Access

A Voucher Ticket Abort or Null

symbol is present on the Up or

the Dn Ports

410 Head Symbol on the Ring

The Controller regenerates head symbols to mark the start

of packets that it introduces to the ring The head symbol is

regenerated from the head written by the client at the trans-

mit port The number of heads that appear on the ring has

no guaranteed relationship to the number of heads loaded

at the transmit port Head symbols on the ring carry informa-

tion in the connection source target and hop fields Table

45 shows the field format for the head symbols on the ring

ports

TABLE 45 Packet Head Format at the Ring Ports

Type F 3130 2928 2724 2320 1916 1512 118

Conn Srce

Trgt Hop 1 Hop 2 Hop 3 Hop 4 Hop 5

411 Payload Symbols on the Ring

A type field of 1 identifies the symbol field as a payload

symbol A payload is 33 bits wide The frame bit distin-

guishes frame from data symbols Tables 46 and 47 show

the field format for payload symbols on the ring

TABLE 46 Data Payload Format at the Ring Ports

T(10)

310

Data Symbol

TABLE 47 Frame Payload Format at the Ring Ports

T(10)

310

Frame Symbol

412 Tall Symbol on the Ring

A type field of 2 identifies the symbol field as a tail symbol

which is nothing else but the last payload symbol of a pack-

et A tail may carry frame or data as determined by the

state of the frame bit These format of these symbol are

shown in Tables 48 and 49

TABLE 48 Tall-Data Format at the Ring Ports

T(10)

310

Data Symbol Acting as a Packet Trail

TABLE 49 Tail-Frame Format at the Ring Ports

T(10)

310

Frame Symbol Acting as a Packet Trail

413 Access Symbols on the Ring

The fourth kind of symbols depicted by a type field of 3 are

access symbols There are four kinds of access symbols on

the ring vouchers tickets nulls and aborts These are

identified in Table 410 through 413

Voucher

Vouchers are sent by source nodes to obtain per-

mission to launch packets of client generated payload sym-

bols QuickRing will send a voucher as soon as there is a

head and a data are loaded at the transmit port Table 410

shows the format for a voucher A Type field value of 3

indicating an access symbol and the ACCess field value of 1

indicates that the symbol is a voucher

TABLE 410 Ring Port Voucher Field Format

Type F 3130 2928 2724 2320 1916 1512 118

Conn Srce

Trgt Hop 1 Hop 2 Hop 3 Hop 4 Hop 5

Ticket

Tickets are returned by target nodes in response to

vouchers They indicate that the target has reserved FIFO

space for one packet QuickRing will send one packet upon

receipt of one ticket The format for a ticket is shown in

Table 411 As in all access symbols the type filed has a

value of 3 In tickets a value of 2 in the ACCess indicates

that the symbol is in fact a ticket

TABLE 411 Ring Port Ticket Field Format

Type F 3130 2928 2724 2320 1916 1512 118

Conn Srce

Trgt Hop 1 Hop 2 Hop 3 Hop 4 Hop 5

Null

Null symbols are sent to consume idle time on the ring

The symbol format is shown in Table 412 When ever a

controller does not have any payload or other access sym-

bol to send it will send a null symbol at its downstream port

TABLE 412 Ring Port Null Field Format

T(10)

3130

290

XXX

Abort

An abort symbol is sent by any node that detects a

failure of addressing protocol or data integrity during nor-

mal operation the QuickRing ring The symbol format is

shown in Table 413

TABLE 413 Ring Port Abort Field Format

T(10)

3130

2918

XXX

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