Advantech PCLS-848-P, Руководство пользователя

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CHAPTER 2 INSTALLATION 15
CHAVIJER 3. PROGRAM~NGREFERENCE
3.1. Introduction
This IEEE-488 interface card contains resident firmware and the library of IEEE-488
procedures those provide IEEE-488 language extensions for the Pascal programs on
your PC. The firmware (software programmed into a ROM) appears transparent to
the users and the code inside is called by the IEEE-488 procedures.
All of the firmware routines are written in assembly language to insure maximum data
transfer rates. Each routine combines bus error checking. The routines also check
parameter values to insure that appropriate bus protocol is followed.
The assembly language routines transfer commands and data on the IEEE-488 BUS
through the use of IEEE-488 procedures that are given English language names such as
icoutput( ), ieenter( ) and ieinit( ). icoutput( ) sends a data string to the IEEE-488 BUS
in much the same way as < writeln(outstring); > sends data to the screen ieenter( )
looks for data coming from the IEEE-488 BUS, similar to the way < readln(instring) >
waits for a keyboard entry to assign to the string variable. icinit( ) clears the interface
and sets up specific operating modes on the interface card as the CLS clears the screen
and establishes specific operating conditions.
The data strings that you include in an iesend( ) procedure can be as general as the
strings you would use in a <write> statement. The iesend( ) procedure interprets
IEEE-488 commands and data in any order that you choose. It also allows you to
build powerful procedure that can be assigned to a single string variable that has a
name and purpose that is meaningful to you. The IEEE-488 BUS commands are
separated by one or more spaces. There is no difficult syntax to learn and only
industry standard mnemonics are used, Because the iesend( ) function recognizes
industry standard mnemonics, it is often possible for you to use manufacturers’
examples directly in your program. This feature also allows you to write professional-
ly documented programs that can be directly cross referenced with the IEEE-488
standard. The function of each mnemonic is performed exactly as defined in the IEEE-
488-1978 standard.