Measurement Computing Personal488 rev.3.0 For DOS & Windows 3.Xi - Manual (Page 61)

8C. External Device Interfacing II. SOFTWARE GUIDES - 8. Driver488/DRV
II-46 Personal488 User’s Manual, Rev. 3.0
Introduction
This Sub-Chapter is a technical review of external device interfacing. It contains information on how
to use external devices, DOS devices and multiple interfaces.
Driver488/DRV controls I/O interfaces and their attached external devices. In turn, Driver488/DRV is
controlled by one of two access methods: the Character Command Language (CCL), and direct DOS
I/O devices.
Driver488/DRV communicates directly with I/O interfaces, such as an IEEE 488 interface board and a
serial (RS-232) port. More than one I/O interface may reside on a single plug-in board. For example,
an RS-232 board often contains two or four functionally separate I/O interfaces, one for each port. The
GP488B board contains the IEEE 488 I/O interface; and an MP488CT board contains an IEEE 488
interface, a digital I/O interface, and a counter/timer I/O interface.
I/O interfaces connect to external devices such as: digitizers, multimeters, plotters, and oscilloscopes
(IEEE 488 interface); and serial devices such as printers, plotters, and modems (serial RS-232 port).
Driver488/DRV allows direct control of IEEE 488 external devices, but it does not support other
external devices such as an RS-232 plotter. Such devices are supported by directly controlling the I/O
interface (serial port).
Driver488/DRV is controlled by sending data and commands, and receiving responses and status by
one of two access methods: the Character Command Language, and Direct DOS I/O devices. These
methods, also known as Application Program Interfaces or APIs, are available to connect the
application (user’s) program to Driver488/DRV.
Character Command Language (CCL)
The Character Command Language (CCL) API is a type of DOS device driver that can control and
communicate with Driver488/DRV. A DOS device driver is a special type of program that appears to
the user’s program as a file that can be written to and read from like any disk file, but that does not
actually read and write the disk. For example, the DOS command:
COPY FILE.LST LPT1
copies the disk file FILE.LST to the device driver LPT1 which prints FILE.LST . There is no file
named LPT1 ; the LPT1 device driver program has the responsibility for communicating with the
printer. The COPY command can write to LPT1 just like an ordinary file, but DOS knows LPT1 is only
a device driver and allows it to process the data.
8C. External Device Interfacing
Topics
•
Introduction..................................................................................... II-45
•
Character Command Language (CCL) ...................................... II-45
•
DOS Devices..................................................................................... II-46
•
Configuration of Named Devices ................................................ II-46
•
Use of External Devices................................................................. II-47
•
Direct I/O with DOS Devices ........................................................ II-47
•
Extensions For Multiple Interfaces............................................ II-48
Duplicate Device Names............................................................................... II-48
Access of Multiple Interfaces ....................................................................... II-48
Example .......................................................................................................... II-49