EasyManuals Logo

ZiLOG System 8000 Hardware Reference Manual

Default Icon
366 pages
To Next Page IconTo Next Page
To Next Page IconTo Next Page
To Previous Page IconTo Previous Page
To Previous Page IconTo Previous Page
Page #115 background imageLoading...
Page #115 background image
HRM
Zilog
Table
4-14
Command
and Command-Status
Registers
HRM
REGISTER
ADDRESS
xxOO
xX01
xx02
xX03
xX04
xX05
xx06
xX07
xX08
xxog
NAME
Command
Register
Unit
Register
Head
Register
Cylinder
Address
Low
Register
Cylinder
Address
High
Register
Sector
Register
Reserved
Reserved
Transfer
Word
Count
8i
ts
7
to
0
Transfer
Word
Count
:B
its
15
to
·3
DEFINITION
The
CPU
sends
specific
commands
to
the
controller
through
this
register.
This
must
be
the
last
register
the
CPU
writes
too,
for
it
clears
the
status
byte
to
enable
handshaking
between
th~
CPU
and
the
controller
and
begins
the
operation.
The
CPU
uses
this
register
to
specify
which
unit
(drive)
it
wants
to
participate
in
I/O
activity.
One
of
four
drives
(0,
1,2,
or
3)
can
be
specified.
The
CPU
uses
this
register
to
specify
the
read-write
head
it
wants
for
the
current
operation.
The
C·PU
stores
the
lo\.-.r-order 8
bits
(7
to
0)
of
the
16-bit
cylinder
address
in
this
register.
The
CPU
stores
the
high-order
8
bits
(15
to
8)
of
the
cylinder
address
in
this
register.
With
the
aurrent
disk
drives,
only
bits
8
and
9
are
used.
The
CPU
stores
in
this
register
the
number
of
the
sector
it
wants
to
read
from
or
write
to.
For
expansion
For
expansion
This
register
contains
the
loworder
byte
of
the
transfer
word
count.
This
register
contains
the
highorder
byte
of
the
transfer
word
count.
4-22
Zilog
4-22

Table of Contents

Other manuals for ZiLOG System 8000

Preview: User Manual
User Manual65 pages

Questions and Answers:

Question and Answer IconNeed help?

Do you have a question about the ZiLOG System 8000 and is the answer not in the manual?

ZiLOG System 8000 Specifications

General IconGeneral
BrandZiLOG
ModelSystem 8000
CategoryDesktop
LanguageEnglish

Related product manuals