User guide

8: Client Applications — DLI Overview
DC 900-1338I 155
8.3 Overview of DLI Functions
After the protocol software is downloaded to the ICP, the client and ICP can commu-
nicate 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.
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, dlWrite, dlRead)
• Send requests and data using dlWrite
• Receive responses using dlRead
• 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
• For server-resident applications, use dlPost before relinquishing task control
• Shut down communications (dlBufFree, dlClose, dlTerm)
Ta bl e 8 –5 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.
Chapter 9 describes the
dlWrite and dlRead functions. Both functions use the optional
arguments parameter to provide the protocol-specific information required for Raw
operation (see Section 8.1.1.1 on page 143). The “C” definition of the optional argu-
ments is described in Section 9.1 on page 157.