Measurement Computing Personal488 rev.3.0 For DOS & Windows 3.Xi - Manual (Page 64)

II. SOFTWARE GUIDES - 8. Driver488/DRV 8C. External Device Interfacing
Personal488 User’s Manual, Rev. 3.0 II-49
530 PRINT ST$ ‘and display it
Once a named device is configured, standard DOS commands may be used to transfer data to that
device. For example:
COPY PLOTFILE.DAT PLOT
copies the plot data file PLOTFILE.DAT to the IEEE 488 bus plotter.
CAUTION
Because named devices can be used as files, some care must be taken so that they do not interfere
with other file or device names in the system:
1. Device names should not be the same as the primary name (the part before the period) of any
existing files or directories. For example, if you define a device with the name “BASIC”,
then you cannot use the program “
BASIC.EXE ”, and if you name a device “IEEE 488", then
you cannot access the Driver488/DRV subdirectory.
2. Device names should not be one of the standard DOS device names: COM, AUX, CON, LPT,
or PRN. This could interfere with normal DOS operation.
3. Device names should normally not be duplicated. If duplicate device names are used, only
the last one of them installed is accessible. To avoid confusion, duplicate device names are
not recommended.
With the considerations noted in the above warning, External Devices and DOS Devices make
Driver488/DRV significantly easier to use. External Devices allow IEEE 488 bus devices to be
referenced symbolically, by a name, rather than by their bus address. They also automatically use the
appropriate IEEE 488 bus terminators and time out period. Finally, it is possible to communicate
directly with DOS Devices just as you would communicate with any file.
Extensions For Multiple Interfaces
Driver488/DRV allows the simultaneous control of multiple interfaces each with several attached
devices. To avoid confusion, external devices may be referred to by their “full name” which consists of
two parts. The “first name” is the hardware interface
name , followed by a colon separator ( : ). The
“last name” is the external device name on that interface. For example, the “full name” of DMM might
be IEEE:DMM .
Duplicate Device Names
Duplicate device names are most often used in systems that consist of several identical sets of
equipment. For example, a test set might consist of a signal generator and an oscilloscope. If three test
sets were controlled by a single computer using three separate IEEE 488 interfaces, then each signal
generator and each oscilloscope might be given the same name and the program would specify which
test set to use by opening the correct interface (
OPEN“IEEE” for one, OPEN“IEEE2" for the other), or
by using the interface names when communicating with the devices ( ”IEEE:GENERATOR" for one and
“IEEE2:GENERATOR” for the other.)
Unique names are appropriate when the devices work together, even if more than one interface is used.
If two different oscilloscopes, on two different interfaces are used as part of the same system, then they
would each be given a name appropriate to its function. This avoids confusion and eliminates the need
to specify the interface when opening the devices.
Access of Multiple Interfaces
If the computer only has one IEEE 488 interface, then there is no confusion, for every external device
is known to be on that interface. However, if the computer has more than one IEEE 488 interface, then
rules apply when using the Character Command Language: