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Ethernet Developers Guide

840 USE 115 00 Version 1.0

The receive state machine

(

which is described below

)

processes the response to a

uest. When the receive state machine has completed receivin

the response, it

chan

es the transmit state machine from the TX_DONE state to the WAIT_TO_TX

state.

Recall that the TransmitUserRe

uest saves the time. CSample_View

OnPollInterval uses this saved time to determine if a new re

uest needs to be

transmitted. OnPollInterval is called b

MFC architectural framework to process

the WM_POLL_INTERVAL sent when CMainFram class processes the window

timer messa

e, WM_TIMER. OnPollInterval examines the transmit state. If the

transmit state is WAIT_TO_TX, and the elapsed time from the previous transmit

uest exceeds the poll interval, then OnPollInterval calls TransmitUserRe

uest to

start another transaction.

B.11 Receive State Machine

The receive state machine receives a response to a transaction b

first readin

the

header, determinin

the size of the rest of the messa

e, and then readin

the bod

of the messa

e. The different states of the receive state machine are as follows.

RX_HEADER. In the RX_HEADER state, the receive machine is receivin

the

messa

e header.

RX_BODY. In the RX_HEADER state, the receive machine is receivin

the

response messa

e associated to the re

uested transaction.

DUMP_BODY. In the DUMP_BODY state, the receive messa

e is receivin

messa

e, but there is no associated transaction with respect to this messa

The window socket DLL

enerates the FD_READ event whenever there is data to

be read. If onl

part of the data is read, it

enerates another event. CSample_View

OnTcpIpRead function processes the FD_READ event, and drives the receive

state machine.

When a FD_READ event is

enerated it is possible that the complete messa

e is

not present. The remote node ma

have attempted to send a 100 b

te response,

but the transport s

stem ma

have onl

had buffer space to transmit three b

tes.

The receiver will

et a FD_READ for the three b

tes. OnTcpIpRead calls

CSample_View rx_ms

to read the receive data into the buffer. There are three

parameters to rx_ms

. The first parameter is a pointer to a receive buffer. The

second input parameter is the receive size. The third parameter is both an input

and output parameter. On both input and output the third parameter is the number

of b

tes read. These parameters allow the processin

of a partiall

received

messa

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