Controller Secondaries Coding Summary - HP 7925D Service Manual

7925
(ATN)
8
PRIMARY 1
I
1
(ATN)
8
I
SECONDARY
!
8
DATA BYTES*
I
1
(ATN)
8
PRIMARY 2
I
*
The number of data bytes may vary from 0 to n,
depending on the particular sequence.
7300-112
Figure A-26. Sequence Protocol
An HP-IB secondary command is associated with each of
the above types. Upon receipt of such a secondary, the
controller examines the modifier field (see table A-15) in
order to distinguish which of the four operation types to
perform.
Appendix A
In addition to the four types of information listed above,
there are seven other types of control information with
secondaries that the controller is capable of interpreting.
These are listed below and described in the following
paragraphs.
• DSJ (DEVICE SPECIFIED JUMP). Informs the I/O
channel whether or not an operation was completed
successfully (a go/no go indication).
• PARALLEL POLL. The I/O channel conducts a paral-
lel poll on the
HP~IB
and each device on the bus is
allowed to request attention or service by asserting
the HP-IB End or Identify (EOD line corresponding to
the HP-IB address.
• SECONDARY (HARD) CLEAR. The controller is
commanded to place itself in a known reset state.
• SELF-TEST. The I/O channel commands the control-
ler to execute a self-diagnostic procedure. The channel
can. then request the result of the diagnostic.
• LOOPBACK. A test of the channel and the controller.
The channel writes data to the controller, then reads
it back and compares it with the original data.
• IDENTIFY. Invoked by the operating system to de-
termine what ,kind of devices are present on the I/O
channel. The controller returns two bytes of preas-
signed identification code whenever the identify is
performed (usually at system power-up) to aid the
channel in the process of auto-configuration.
Table A-15. Controller Secondaries Coding Summary
SECONDARY COMMAND
PRIMARY SECONDARY %
MODIFIER
FUNCTION
COMMAND
TYPE
FIELD
8
7 6 5 4 3 2 1
Listen
D (DATA)
P 1 1
0
1
0 0 0
Receive Disc Command (Secondary Get Command)
Talk
D P
1 1 0 1 0 0 0
Send Disc Status (Secondary Send Status)
Listen D
P 1
1 0 0 0 0 0
Receive Write Data (Secondary Write Data)
Talk
D P
1 1 0 0 0 0 0
Send Read Data (Secondary Read Data)
Listen
D P
1 1 0 1 0 0 1
Cyclic Redundancy Check (CRC)"
Talk D
P 1 1
0 1
0
0 1
Cyclic Redundancy Check (CRC)"
Listen C (CONTROL) P
1 1 1 0 0 0 0
Secondary (Hard) Clear
Talk
C P 1 1 1
0 0 0 0
Return Device-Specified Jump (DSJ) byte
Listen C
P 1 1 1
1
1
1 1
Initiate Self-Test
Talk
C P
1 1 1 1
1 1 1
Return Self-Test Result
Listen C
P 1 1 1 1
1 1 0
Write Loopback Record
Talk
C P
1 1 1 1 1 1 0
Read Loopback Record
Untalk
-
P 1 1 A D
D R S
Identify
" Not implemented on current versions of the controller.
A-83