National Instruments GPIB-SCSI-A, Руководство пользователя

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© National Instruments Corp. 7-1 GPIB-SCSI-A User Manual
Chapter 7
G Mode Functions
This chapter contains a detailed description of each G mode function. The
functions are in alphabetical order for easy reference and each function
contains its syntax and purpose, as well as some examples.
Points to Remember
Consider the following points when reading through the G mode functions:
• In the function syntax descriptions, arguments shown in square
brackets (
[]
) are optional. Do not enter the brackets as part of your
argument.
• Terminate each programming message with a carriage return (<CR>), a
linefeed (<LF>), a carriage return followed by a linefeed (<CR><LF>),
or vice versa (<LF><CR>). This is denoted by <CR> in the syntax
portions of the function descriptions and by
'\n'
in the C examples.
• It is necessary for you to send only enough characters of the function
name to distinguish it from other functions. These characters are
shown in boldface in the syntax portion of the function descriptions.
• Functions listed as low-level give you the ability to work with most any
SCSI device, no matter how complex, as long as you are aware of how
the SCSI device handles phase changes and information transfer. High-
level functions allow the GPIB-SCSI-A to handle all the required
phases as well as all information transfers without user intervention.
You should try to communicate with your devices through the high-
level functions as they work faster than the low-level since only one
command interpretation is necessary for a complete request. Whereas,
with low-level commands, you must request several commands to
complete one SCSI request.
• Even though the functions may be called by another name, if the values
comprising the Command Descriptor Block created by the high-level
command are identical to what is expected by a device for some other
activity, there is nothing wrong with using the function if the phases