Schneider Automation Modicon Quantum Ethernet Podręcznik Użytkownika Pobierz pdf (Strona 82)

Ethernet Developers Guide

840 USE 115 00 Version 1.0

B.10 Transmit State Machine

The transmit state machine establishes a connection, and periodicall

transmits a

uest. The different states for the transmit state machine are as follows.

IDLE. In the IDLE state, there is no connection.

RESOLVING_NAME. In the RESOLVING_NAME state, CSample_View is

waitin

for the window socket DLL to convert a node’s name into an IP

address.

CONNECTING. In the CONNECTING state, CSample_View is waitin

for the

window socket DLL to

enerate the FD_CONNECT event. This event

indicates if the attempt to establish a connection succeeded or failed.

CONNECTED. The CONNECTED state indicates that a connection has been

successfull

established.

WAIT_TO_TX. In the WAIT_TO_TX state, CSample_View is waitin

transmit the messa

e. It transmits the messa

e, when the time from the last

transmit exceeds the specified poll interval.

BLOCKED. When CSample_View attempts to send a messa

e, the window

socket DLL ma

not be able to transmit the complete messa

e. This is a flow

control condition, and CSample_View enters the BLOCKED state. The

window socket DLL

enerates the FD_WRITE event when it can send more

data.

TX_DONE. CSample_View enters the TX_DONE when it has completed

transmittin

the re

uest.

If the CSample_View is in the IDLE state, and user selects either the connect menu

item, or the connect tool bar button, CSample_View OnMana

Connect function

attempts to establish connect with its tcpip_initate_connection function. This

function examines the remote destination and determines if it’s a name or an IP

address. If it’s a name, OnMan

Connect chan

es the transmit state to

RESOLVING_NAME, and it invokes the window sockets DLL

WSAAs

ncGetHostB

Name function to resolve the name. Window sockets DLL

will

enerate the user defined WM_TCPIP_NAME_RESOLVED messa

e which

indicates if the name has been resolved. The OnTcpIpNameResolved member

function process the WM_TCPIP_NAME_RESOLVED messa

e. If the name is not

resolved, OnTcpIpNameResolved chan

es the transmit state back to IDLE.

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