User`s guide

2: DDCMP DLI Functions

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2.4 Overview of DLI Functions for DDCMP

After the DDCMP software is downloaded to the Freeway ICP, the client and Freeway

can communicate by exchanging messages. These messages conﬁgure and activate each

ICP link and transfer data. The client application issues reads and writes to transfer

messages to and from the ICP.

Caution

When using non-blocking I/O, there must always be at least one

dlRead request queued to avoid loss of data or responses from the

ICP.

This section summarizes the DLI functions used in writing a client application. An

overview of using the DLI functions is:

• Start up communications (dlInit, dlOpen, dlBufAlloc)

• Send requests and data using dlWrite

• Receive responses using dlRea

• For blocking I/O, use dlSyncSelect to query read availability status for multiple

sessions

• For non-blocking I/O, handle I/O completions at the software interrupt level in

the completion handler established by the

dlInit or dlOpen function, or by

periodic use of

dlPoll to query the I/O completion status

• Monitor errors using dlpErrString

• If necessary, reset and download the protocol software to the ICP using dlControl

• Shut down communications (dlBufFree, dlClose, dlTerm)

Table 2–4 summarizes the DLI function syntax and parameters, listed in the most likely

calling order. Refer to the Freeway Data Link Interface Reference Guide for details.