User`s manual

10 PCL-848AB User's Manual
3. PROGRAMMING REFERENCE
3.1. Introduction
The PCL-848A/B interface card contains the resident firmware that provides IEEE-
488 language extensions for your PC. The firmware (software programmed into a read-
only-memory) appears transparent to the users and the function inside is called by the
IEEE-488 commands.
All of the routines in the firmware are written in assembly language to insure maxi-
mum data transfer rates. Each routine combines bus error checking. The routines also
check parameter values to insure that appropriate bus protocol is followed.
The routines in the firmware transfer commands and data on the IEEE-488 BUS
through the use of statements that are given English I language names like OUTPUT,
ENTER and INIT. Statement OUTPUT sends a data string to the IEEE-488 BUS in
much the same way as <PRINT “string”> sends data to the screen. Statement ENTER
looks ] for data coming from the IEEE-488 BUS, similar to the way <INPUT X$>
waits for a keyboard entry to assign to the string variable X$. Statement INIT 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 a SEND statement can be as general as the strings
you would use in a <PRINT> statement. The SEND function interprets IEEE-488
commands and data in any order that you choose. It also allows you to build powerful
commands 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 standard IEEE-488
mnemonics are used. The function of each mnemonic is performed exactly as defined
in the IEEE-488-1978 standard.
The firmware converts your command and data strings to specific control codes for
the IEEE-488 bus controller chip. It also passes back received data and interface status
conditions to your program. Received information may be used directly by your
program and the status codes (those returned by the STATUS function) may be used
to determine various interface operating conditions or to detect syntax errors in the
statements.
The next section discusses the CALL statement of BASICA and QuickBASIC. All of
the examples are given in BASICA, the syntax and use of each function is similar to
those of QuickBASIC version 2.0, 3.0 and 4.0.