Establishing communications – Measurement Computing Personal488 rev.3.0 For DOS & Windows 3.Xi User Manual

Page 183

9G. Pascal

II. SOFTWARE GUIDES - 9. Driver488/SUB

II-168

Personal488 User’s Manual, Rev. 3.0

The following declarations are assumed throughout the remainder of this discussion.

var
adc,ieee,dev,adc2 : Integer;

{ Device handles }

code : Integer;

{ Return Code }

hundred : array [0..99] of Integer;

{ Driver488/SUB status structure }

response : string;

{ Text buffer for Driver488/SUB responses }

i: Integer;

{ General purpose loop counter }

voltage : Real;

{ Single reading variable }

sum : Real;

{ Summation used to compute average }

substat : IeeeStatusrec;

{ Driver488/SUB status structure }

nilptr : pointer;

{ General purpose pointer }

lrv : Longint;

{ General purpose long return value }

sp,stadc,

{ Driver488/SUB and ADC488 spoll response }

errnum : Integer;

{ ADC488 error number }

errtext : string;

{ ADC488 error response }

Establishing Communications

For the sake of this discussion, assume that Driver488/SUB has been configured to start with a
configuration including the devices

IEEE

(IEEE 488 interface) and

ADC

(an ADC488/8S connected to

the IEEE 488 interface). Additional interfaces and/or devices may also have been defined, as the driver
can support up to four interfaces and 56 devices simultaneously. To open the two devices of interest,
we use the following statements:

ieee: = ioOpenName (‘IEEE’);
adc: = ioOpenName (‘ADC’);

If the

ADC

was not configured within Driver488/SUB, it can be optionally created “on the fly.” First,

verify that opening the

ADC

failed, then use the

GetError

command to clear the error condition

generated by this failure. Next, use the handle of the device

DEVIEEE

, which is always available within

Driver488/SUB, to clone a new device called

ADC

using the

MakeDevice

command. Lastly, the IEEE

bus address

is assigned to the

ADC

if adc = -1 then begin

rv: = ioGetError (ieee, response);
dev: = ioOpenName (‘DEVIEEE’);
adc: = ioMakeDevice (dev,’ADC’);
rv: = ioBusAddress (adc,14,-1);

end;

If other devices were needed for the application at hand, they could either be defined in the startup
configuration for Driver488/SUB or they could be created “on the fly” from the application:

dev: = ioOpenName (‘DEVIEEE’);
adc2: = ioMakeDevice (dev,’ADC2’) ;
rv: = ioBusAddress (adc2,14,-1) ;

The new device

ADC2

is configured to reside at a different bus address so that the two devices may be

distinguished. There is one other important difference between

ADC

and

ADC2

at this point.

ADC2

is a

temporary device; that is, as soon as the creating application closes,

ADC2

ceases to exist. If our intent

was to create a device that could be accessed after this application ends, we must tell Driver488/SUB
this:

rv: = ioKeepDevice (adc2);

After executing the above statement,

ADC2

is marked as being permanent; that is, the device will not be

removed when the creating application exists. If we later wish to remove the device, however, we can
do so explicitly:

rv: = ioRemoveDevice% (adc2);