National Instruments GPIB-SCSI-A, Руководство пользователя

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Chapter 7 G Mode Functions
© National Instruments Corp. 7-29 GPIB-SCSI-A User Manual
hcmd - Execute a High-Level SCSI Command
Type: SCSI function
Syntax:
hcmd command bytes
<CR>
hcmd command bytes, i count
<CR>
hcmd command bytes, o count
<CR>
Purpose: Use
hcmd
if you want to issue a high-level SCSI command,
but that command is not provided in the high-level functions
of the GPIB-SCSI-A.
Remarks: This function is used to process an entire high-level SCSI
command. It handles all of the needed SCSI phases for any
SCSI command, including data transfer.
command bytes
indicates the bytes to go into the Command
Descriptor Block. If nothing follows the
command bytes
,
the command does not require a Data In or Data Out phase. If
a Data In phase is required, the
command bytes
should be
followed by
i count
. If a Data Out phase is required, the
command bytes
should be followed by
o count
.
count
represents a 32-bit unsigned number. It is the number
of bytes that the user expects the GPIB-SCSI-A to transfer
during the Data In or Data Out phases. Correct values range
from 1 to 4,294,967,295. During commands that require a
Data Out phase, if this count is not met, the value specified by
the
pad
command is used to pad the transfer to the requested
count.
If during the execution of this command, the GPIB-SCSI-A
encounters a phase which it did not expect, an EPHS error
indication results. For a list of the expected phases, refer to
the section titled Handling of SCSI Phases in G Mode in
Chapter 6, Programming in G Mode.
The
command bytes
go into the Command Descriptor
Block in the order that you enter them – that is, if you enter