Chapter 6
Programming in G Mode
© National Instruments Corp.
6-7
GPIB-SCSI-A User Manual
Once you have completed steps 1 and 2, the GPIB-SCSI-A performs the
following:
1.
The GPIB-SCSI-A automatically handles the arbitration for the SCSI
bus, the selection of the disk drive at Target ID 4, and waits for data
from the Data Channel. Any of this data is sent directly to the SCSI
device.
2.
When all of the data has been sent, the GPIB-SCSI-A automatically
handles the final Status and Message In phases that the disk drive
creates to complete the transfer.
3.
The information bytes received from the Status and Message In phases
are stored in a buffer in the GPIB-SCSI-A and can be retrieved by
reading GPIB data from the Command and Status Channel.
The LISTEN LED on the GPIB-SCSI-A front panel is lit when the
GPIB-SCSI-A is addressed to listen.
The GPIB-SCSI-A and SCSI System as Talker
When the GPIB-SCSI-A receives the Command and Status Channel talk
address, it sends out status information that has been buffered. This can be
either the SCSI Status phase and Message In phase information or, if you
have enabled status reporting with the
stat
command, the internal status
of the GPIB-SCSI-A.
When the GPIB-SCSI-A receives the Data Channel talk address, it sends all
data received from the SCSI during the Data In phase to the GPIB.
Because the GPIB-SCSI-A can communicate with any SCSI device in the
SCSI system of which the GPIB-SCSI-A is a part, one of the first
requirements is that you indicate to the GPIB-SCSI-A the Target ID of the
SCSI device with which you want to communicate by using
tid
. After
using
tid
, any other request made to the GPIB-SCSI-A that causes
communication with the SCSI system is made to the device with a SCSI
Target ID set by
tid
.
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Страница 355: ...Appendix C Operation of the GPIB National Instruments Corp C 7 GPIB SCSI A User Manual Figure C 2 Linear Configuration ...
Страница 356: ...Operation of the GPIB Appendix C GPIB SCSI A User Manual C 8 National Instruments Corp Figure C 3 Star Configuration ...