Chapter 5
S Mode Functions
© National Instruments Corp.
5-47
GPIB-SCSI-A User Manual
lines - Return the State of the Eight GPIB Control
Lines
Type:
Bus Management function
Purpose:
This command is used to determine the state of the eight GPIB
control lines.
Format:
Bit
7
6
5
4
3
2
1
0
Byte
0
Opcode = C3H
1
Reserved
2
Reserved
3
Reserved
4
Reserved
5
Reserved
Remarks:
This command returns two bytes of information. The state of
the eight GPIB control lines is returned in the first byte, as
follows :
7
6
5
4
3
2
1
0
EOI
ATN SRQ REN IFC NRFD NDAC DAV
The second byte contains mask bits in the same order as
above, indicating which lines are actually being reported,
and which are undeterminable. If a particular mask bit is
1, then the corresponding bit in the first byte indicates the
state of that line. If the mask bit is 0, then the
corresponding bit in the first byte should be disregarded.
The information transfer phases that the GPIB-SCSI-A drives
the SCSI through after selection are the Command, Data In,
Status, and Message In phases.
