DP83261AVF datasheet(92/132 Pages) NSC

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70 Signal Descriptions (Continued)

Handshake

The Handshake signals control the Request Interface handshaking process They are used for token capture and transmission

of PDUs

Symbol

Description

TXPASS

Transmit Pass

Indicates the absence of a Service Opportunity This could result from an unusable

request class waiting for a token timer expiration or MAC Reset TXPASS is always asserted between

service opportunities It is deasserted when TXRDY signal is asserted at the beginning of a Service

Opportunity

TXRDY

Transmit Ready

Indicates that the Transmitter is ready for another frame For a non-immediate

request a usable token must be held in order to transmit frames TXRDY is asserted when

a) A usable token is being held or

b) An immediate request becomes serviceable or

c) After frame transmission if the current Service Opportunity is still usable for another frame

It is deasserted when the TXPASS or TXACK signal is asserted

RQRDY

Request Ready

Indicates that the Transmitter should attempt to provide a Service Opportunity as

indicated by the RQRCLS(3 – 0) signals one cycle before RQRDY is asserted The Service Opportunity

will be maintained as long as possible If RQRDY is asserted within 6 byte times after TXRDY signal is

asserted the Transmitter will wait at least L

Max plus one Void frame (416 ms or 480 ms) for

RQSEND to be asserted before releasing the token

RQSEND

Request Send

Indicates that the Transmitter should send the next frame The MRD(7 – 0) signals

convey the FC byte when the RQSEND signal is asserted If RQSEND is asserted within 6 byte times

after the TXRDY signal is asserted the Transmitter will send the frame with a minimum length

preamble If RQSEND is not asserted within L

Max plus one Void frame after RQRDY signal has been

asserted (416 ms or 460 ms) the token may become unusable (due to a timer expiration)

For Immediate transmissions from the Claim or Beacon State (when RQCLM or RQBCN is asserted)

RQSEND must be asserted no later than 8 byte times after TXRDY is asserted

RQSEND may only be asserted when TXRDY and RQRDY signals are asserted and RQFINAL is

deasserted RQSEND must be deasserted not later than one byte time after TXRDY is deasserted

TXACK

Transmit Acknowledge

Indicates that the Transmitter is ready for the next data byte TXACK is

asserted when the FC byte is accepted on MRD7 – 0 and remains asserted for each additional data

byte accepted It is deasserted one byte time after RQEOF ro RQABT is asserted The signal is also

deasserted when TXABORT or TXPASS is asserted

RQEOF

Request End of Frame

Indicates that MRD7 – 0 conveys the last data byte when asserted Normally

this is the last byte of the INFO field of the frame (exceptions FCS transparency invalid frame length)

RQEOF causes TXACK to be deasserted and is ignored if TXACK is not asserted

RQABT

Request Abort

Indicates that the current frame should be aborted Normally this causes the

Transmitter to generate a Void Claim or Beacon frame RQABT causes TXACK to be deasserted and

will prevent TXACK assertion The BMAC will ignore RQABT if asserted with RQEOF

RQFINAL

Request Final

Indicates that the final frame of the request has been presented to the MAC Interface

When asserted the Issue Token Class (as opposed to the Capture Token Class) becomes the new

Token Class (TXCLASS) RQFINAL may only be asserted when RQRDY is asserted and RQSEND is

deasserted RQFINAL is ignored unless RQRDY has been asserted for at least one byte time and the

service parameters have been valid for at least three byte times RQFINAL must be deasserted not

later than two byte times after RQSEND is deasserted

DP83261AVF Datasheet(PDF) 92 Page - National Semiconductor (TI)

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