User`s guide

3: FMP DLI Functions

DC 900-1339H 45

3.4 Overview of FMP Requests using dlWrite

For FMP the dlWrite function supports three dlWrite categories: commands, informa-

tion requests, and data transfer, which are discussed in detail in Section 3.4.1 through

Section 3.4.3. Whether you use blocking or non-blocking I/O, each

dlWrite request

must be followed by a

dlRead request to receive the command conﬁrmation, informa-

tion requested, or acknowledgment of the data transfer. Section 3.5 discusses these dif-

ferent responses received using

dlRead.

In a typical FMP application, most

dlWrite requests use Raw operation; that is, the

optional arguments structure (page 44) is required to specify protocol-speciﬁc infor-

mation.

If your application is limited to interacting with Freeway only to exchange data with the

remote application, you can read and write using Normal operation. The

writeType

DLI conﬁguration parameter (Table 5–1 on page 104) speciﬁes the type of data to be

exchanged. If

writeType is set to “normal,” normal data with EOM is used

(Section 3.4.3.1); if

writeType is set to “transparent,” transparent data with EOM is

used (Section 3.4.3.2).

Caution

Take care not to confuse the terms “Normal operation” and “nor-

mal data.” Normal data can be sent using either Normal or Raw

operation.

Table 3–4 shows the FMP DLI request codes for different categories of the

dlWrite

function. Each request is explained in the following sections.

In addition to the command-speciﬁc error codes listed in the following sections, an

unsuccessful

dlWrite function can return one of the following error codes in the dlRead

pOptArgs.iICPStatus field (see Appendix C for error handling):