HP 9845B/C CE Service Manual

A-6 HP 9895A Disc Memory Command Set
Holdoffs
The 9895A will not execute most operations when it enters either of the two states described
below.
It is very important to know these states and the commands that will remove the
holdoffs.
1. DSJ = 2 or Power On State
This state is entered after:
a. The 9895A
is powered up.
b. After the execution of the Initiate Self-Test command.
As long as DSJ = 2, a value unique to this state, the commands listed below will not
be executed. There are, however, three commands which may be executed either to
change the DSJ or override its holdoff. These commands are:
a.
The DSJ command,
b. The Clear commands,
c.
The Cold Load Read command.
For
both DSJ and Clear, the DSJ value becomes 0, the cold load read will override the
holdoff
and set the DSJ according to the outcome of the read.
The only way for the bus controller to realize that the device
was in the Power On state
is by sending the DSJ command (which clears the state).
The purpose of this holdoff state is to withhold all operations that may occur during
normal usage until the bus controller can become aware
that the power has been
interrupted.
The following is a list of the commands not executed while in the DSJ = 2 state:
a.
All Read commands
b.
All Write commands
c. Verify
d. Initialize
e. Format
f. Seek
S. End
h. Request status
i. Request disc address commands
The 9895A will, however, respond to a Talk command from the above group by
sending
one byte (of value I) tagged with an EOL Also, all data bytes sent to the
9895A as part of the
commands listed above will be accepted but ignored. These
actions
will cause the 9895A not to hang (timeout) the HP-IB until the bus controller is
aware of the holdoff.

HP 9845B/C CE Specifications

General

Brand	HP
Model	9845B/C CE
Category	Storage
Language	English