Measurement Computing Personal488 rev.3.0 For DOS & Windows 3.Xi - Manual (Page 227)

10E. C Languages II. SOFTWARE GUIDES - 10. Driver488/W31
II-212 Personal488 User’s Manual, Rev. 3.0
Confirming Communications
With or without an open device handle, the application can, if desired, confirm communication with
Driver488/W31 via the
Hello function:
Hello(ieee, textstr);
strcat(textstr, “\r\n”);
The function also fills in a string, from which information can be extracted if it is desirable to display
facts about the driver in use.
IEEE 488 Event Message
The IEEE 488 Event Message feature of Driver488/W31 allows a C program to respond to IEEE 488
bus events. Driver488/W31 will send the Windows Message
WM_IEEE488EVENT to the application
when an enable event occurs. A listing of available events is shown in the table:
Event Description
SRQ The Service Request bus line is asserted.
Peripheral An addressed status change has occurred and the interface is a Peripheral.
Controller An addressed status change has occurred and the interface is an Active Controller.
Trigger The interface has received a device Trigger command.
Clear The interface has received a device Clear command.
Talk An addressed status change has occurred and the interface is a Talker.
Listen An addressed status change has occurred and the interface is a Listener.
Idle An addressed status change has occurred and the interface is neither a Talker nor a
Listener.
ByteIn The interface has received a data byte.
ByteOut The interface has been configured to output a data byte.
Error A Driver488/W31 error has occurred.
Change The interface has changed its addressed state. The Controller/Peripheral or
Talker/Listener/Idle states of the interface have changed.
Note: This Event table mirrors the Arm Condition table found under the topic “System Controller,
Not Active Controller Mode” in the Sub-Chapter “Operating Modes” of Chapter 9.
To trap the IEEE 488 Event Message: Simply check for the WM_IEEE488EVENT message in the default
switch of the application’s window handler. If the IEEE 488 Event Message is detected, execute code
to handle the event.
The following example uses the capability of the ADC488 to issue an IEEE 488 SRQ when it needs
servicing. The IEEE 488 Event Message will be issued and trapped on the SRQ and the ADC488 will
be serviced.
In every C program using Driver488/W31, header files of declarations must be merged into the
program. In the following example, those declarations have been omitted from the listing for the sake
of brevity.
With the associated source files, the following program can be built using the file EXAMPLE3.MAK (for
Microsoft C or Quick C users) or EXAMPLE3.PRJ (for Borland C users) found on the Driver488/W31
disk.
This example has several declarations that will be used later:
HWND hDriver /* handle for Driver488/W31 */
DevHandleT ieee; /* handle for the IEEE board * /
char textstr[2048], response[64]; /* string for Driver488responses */
char hellomsg[256]; /* string to hold the hello response */
int i, hundred[100]; /* general counter and data buffer */
TermT noterm; /* structure for disabling terminators */
Starting out like the previous example, this program then differs by adding an Error line to turn ON the
automatic error reporting: