DP83261AVF datasheet(93/132 Pages) NSC

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70 Signal Descriptions (Continued)

Service Parameters

The Service Parameters define the Service Request They must be valid for at least one byte time before the RQRDY signal is

asserted and must not change while RDRDY remains asserted See Section 531 for the encoding of RQRCLS

The Requested Service corresponds to the Request Service Class and the Token Class parameters of the

(SM

)MA

DATArequest and (SM

)MA

Tokenrequest primitives as specified in the Standard

Encoded into each of the 14 possible values of RQRCLS in the Service Class (Non-Restricted Asynchronous Restricted

Asynchronous Synchronous Immediate) the Token Capture and Issue Class and THT Enable

Requests are serviced on a Service Opportunity meeting the requested criteria

External support is required to limit the requests presented to the MAC Interface by different MAC Users (SMT LLC etc)

Symbol

Description

RQRCLS(3 – 0)

19 – 22

Request Class

Indicates the Service Class parameters for this request (see Section 531)

When RQRCLS l 0 the Transmitter will capture a usable token (for non-immediate requests)

and assert TXRDY The Service Opportunity continues as long as the token is usable with the

current service parameters even if RQRDY is not asserted If RQRCLS indicates a service class

that is not serviceable for any cycle of a service opportunity the service opportunity will conclude

after the current frame and a token of the issue token class will be issued

If RQRCLS e 0 the Service Opportunity will terminate after the current frame and a token will be

issued (even if RQRCLS subsequently becomes non-zero) See Table 5-3

RQCLM

Request Claim

Indicates that this request is to be serviced in the Claim state Ignored for non-

immediate requests

RQBCN

Request Beacon

Indicates that this request is to be serviced in the Beacon state Ignored for

non-immediate requests

Frame Options

The Frame Options signals are selected for each frame They must be valid while the RQSEND signal is asserted These

options are typically used in bridging applications

Symbol

Description

STRIP

Void Strip

Forces two My

Void frames to be transmitted on end of current Service Opportunity

Stripping continues until a My

Void frame returns If any frame of a Service Opportunity requests this

option then all frames on that Service Opportunity will be stripped using this method

SAT

Source Address Transparency

When SA transparency is selected the SA from the data stream is

transmitted in place of the internal MSA or MLA stored in the MAC Parameter RAM

SAIGT

Source Address IG Transparency

With this option the MSB of the SA is sourced from the data

stream as opposed to being forced to zero

FCST

Frame Check Sequence Transparency

When selected the Ring Engine generated FCS is not

appended to the end of the Information field

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