Measurement Computing Personal488 rev.3.0 For DOS & Windows 3.Xi - Manual (Page 124)

II. SOFTWARE GUIDES - 8. Driver488/DRV 8M. Data Transfers
Personal488 User’s Manual, Rev. 3.0 II-109
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IEEEIO.BAS : Communications routines for Driver488/DRV.
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IEEEIO.ASM : Assembly language file for direct DOS access without Turbo Basic interference.
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IEEEIO.COM : Executable version of IEEEIO.ASM .
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KYBDCTRL.BAS : Turbo Basic version of the Keyboard Controller Program.
The actual demonstration program is contained in 195DEMO.BAS . These examples also require the file
REGNAMES.INC which is included with Turbo Basic.
Terminators
Every transfer of data, between a program and Driver488/DRV, or between Driver488/DRV and a bus
device, must have a definite end. This is a common requirement in most systems. For example, most
printers do not print a line until they receive the carriage return that ends that line. Similarly, a BASIC
INPUT statement waits for the key to be pressed before returning the entered data to the
program. The only time that some terminator is not required is when the number of characters that
compose the data is known in advance or is transferred along with the data. This is the case, for
example, when fixed-length records are read from a random access disk file.
Driver488/DRV actually uses four terminators:
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The end-of-line ( EOL ) terminator for output from the program to Driver488/DRV.
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The end-of-line ( EOL ) terminator for input to the program from Driver488/DRV.
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The data terminator ( TERM ) for output to bus devices from Driver488/DRV.
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The data terminator ( TERM ) to input from bus device into Driver488/DRV.
End-Of-Line (EOL) Terminators
The EOL terminators mark the end of character strings transferred between the user’s program and
Driver488/DRV. The EOL output terminator marks the end of strings transferred from the user’s
program to Driver488/DRV, and the EOL input terminator marks the end of strings transferred into the
user’s program from Driver488/DRV.
The EOL terminators normally consist of one or two ASCII characters. The characters do not need to
be printable. In fact they are usually special characters such as carriage return and line feed. Also,
input and output terminators need not be the same.
It is possible to specify that no characters are to be used as EOL terminators. If the EOL output
terminator is set to NONE , then Driver488/DRV assumes that it receives an entire command in each
8M. Data Transfers
Topics
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Terminators ................................................................................... II-108
End-Of-Line (EOL) Terminators ................................................................II-108
TERM Terminators ......................................................................................II-112
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Direct I/O & Buffered I/O............................................................ II-113
Direct Bus OUTPUT.....................................................................................II-113
Direct Bus ENTER .......................................................................................II-113
Buffered I/O...................................................................................................II-114
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Asynchronous Transfers............................................................. II-115