Asynchronous Serial Communications Programmer's Reference Manual (32022-90052)

48 Chapter2

Controlling Asynchronous Devices Programmatically

MPE/iX System Intrinsics

The MPE/iX system provides a set of subroutines, callable by your

program, that help you interface with the ﬁle system to accomplish

various tasks. These subroutines are an integral, or intrinsic, part of

the operating system, and are therefore referred to as system intrinsics.

Intrinsics exist which allow you to perform a variety of recurring tasks,

ranging from manipulating individual ﬁle attributes to manipulating

processes, if you have the needed capabilities.

Intrinsics are program segments, no different from the code you write

yourself except that they are invisible to you. They are usually coded in

Pascal/iX (system language for HP 3000 Series 900 computers), but are

generally callable from any supported language.

This manual discusses the subset of system intrinsics that are most

useful for dealing with communications between the system and an

asynchronous device. It is intended to provide the reader with a high

level of detail regarding the use of intrinsics for controlling such

devices. A complete description of all the system intrinsics available to

you can be found in the MPE/iX Intrinsics Reference Manual, along

with details regarding their use.

With one exception, the intrinsics described in this manual can be used

in both native mode and compatibility mode programs. The exception is

the HPFOPEN intrinsic, which can be called from native mode

programs only. (There are other MPE/iX intrinsics which can only be

called from native mode programs, but HPFOPEN is the only one

discussed in this manual.)

Intrinsics and Asynchronous Serial

Communications

Certain system intrinsics are particularly useful to you for providing an

interface between the ASC managers that handle serial device

connections and the MPE/iX File System. These are primarily the

intrinsics that provide simple mechanisms for accessing and altering

ﬁles, handling I/O operations, and checking ﬁle status. The following

list provides a summary of these intrinsics and their functions. For a

more complete description of the syntax and use of these intrinsics see

Chapter 8, “Intrinsics Reference.” Additional information about the

practical use of the intrinsics listed here can be found throughout this

manual.