HP 9845B/C CE Service Manual

A-4 HP 9895A Disc Memory Command Set
Target Addressing
Each unit has a target address associated with it. This is the logical address of the next sector
which
will be accessed by a Data Transfer command or return for an address request. This
sector is referred
to as the target sector. It is uniquely determined by a target cylinder
address, a target
head address and a target sector address.
Following a
power up or a Clear command, the target address will be set to cylinder 0, head
° and sector ° for HP format and 1 for IBM format.
A
Seek command sets the target address to the cylinder, head and sector indicated in the
command sequence.
During a
data transfer, the target address is automatically updated so the successive logical
sectors
can be read without issuing a seek to each sector. This includes updates which cross
track
or cylinder bounds. The 9895A is always in cylinder mode; that is, the head address
will be incremented before the cylinder address.
If a data transfer terminates abnormally, the target address is left pointing at the sector which
caused the termination.
The D Bit
Each sector has a flag called the D bit. It is used to indicate that' a track is defective (which is
different than invisible). The D bit can be set or cleared using the Initialize command. A set D
bit affects the Read, Write
and Format commands and is indicated in the returned status.
The Format
command is used to convert all tracks flagged with the D bit into invisible tracks.

HP 9845B/C CE Specifications

General

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