Measurement-computing Personal488 rev.3.0 For DOS & Windows 3.Xi Manual de usuario descargar pdf (Pagina 81)

8G. QuickBASIC II. SOFTWARE GUIDES - 8. Driver488/DRV

II-66 Personal488 User’s Manual, Rev. 3.0

must be opened, one for input, and one for output. Other languages may allow the same file to be

opened for both input and output. Three file names are allowed:

\DEV\IEEEOUT

\DEV\IEEEIN

, and

\DEV\IEEE

. By convention, they are used for output, input, and both input and output, respectively.

But in actuality, they are all the same and any one of them can be used for input, output, or both,

depending on the programming language.

In BASIC, the files are opened with the following commands:

110 OPEN “\DEV\IEEEOUT” FOR OUTPUT AS #1

200 OPEN “\DEV\IEEEIN” FOR INPUT AS #2

Of course, file numbers may change as desired, but throughout this manual, file

is assumed to output

to Driver488/DRV, and file

is assumed to input from Driver488/DRV.

Once these files are opened, we can send commands and receive responses from Driver488/DRV.

While Driver488/DRV should normally be in a reset, inactive state, it is possible that it was left in

some unknown state by a previous program failure or error. In order to force Driver488/DRV into its

quiescent state we can use the

IOCTL

statement:

160 IOCTL#1,"BREAK"

IOCTL

is a BASIC statement that sends commands through a “back door” to Driver488/DRV.

Driver488/DRV recognizes this “back door” command regardless of what else it might be doing and

resets itself so that it is ready to accept a normal command. We can then completely reset the

Driver488/DRV with the

RESET

command:

170 PRINT#1,"RESET"

which resets the operating parameters of the Driver488/DRV back to their normal values (those that

were set during system boot by the

DRVR488

DOS command).

The

IOCTL BREAK

and

RESET

commands guarantee that Driver488/DRV is ready for action. Note

that the

IOCTL BREAK

and

RESET

commands are placed before the

OPEN

statement for file

. This

guarantees that BASIC is able to open Driver488/DRV for input. For more details, see the

FILL

command in “Section III: Command References.”

With the initialization commands and some comments, the program now appears as:

100 ‘Establish communications with Driver488/DRV

110 OPEN “\DEV\IEEEOUT” FOR OUTPUT AS #1

120 ‘

150 ‘Reset Driver488/DRV

160 IOCTL#1,"BREAK"

170 PRINT#1,"RESET"

180 ‘

190 ‘Open file to read responses from Driver488/DRV

200 OPEN “\DEV\IEEEIN” FOR INPUT AS #2

Once everything is reset, we can enable the

SEQUENCE - NO DATA AVAILABLE

error detection by

setting the

FILL

mode to

ERROR

225 PRINT#1,"FILL ERROR"

We can also test the communications and read the Driver488/DRV revision number with the

HELLO

command:

310 PRINT#1,"HELLO"

320 INPUT#2,A$

330 PRINT A$

First we

the

HELLO

command to file

, then we

INPUT

the response from file

into the

character string variable

(“A-string”). Finally we display the response with a

to the screen.

Because BASIC cannot both

and

INPUT

from the same file, we use two

OPEN

statements, and

two different file numbers to communicate with Driver488/DRV.

must reference the file

opened for output (in these examples, file

) and

INPUT

must reference the file opened for input (file

). Attempting to communicate with the wrong file (such as

INPUT#1

) results in an error.

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