HRM
Zilog
HRM
In
addition
to
these
registers,
the
host
communicates
with
the
controller
via
a
Dispatch
Table
and
Packets
(one
per
disk
unit)
in
host
memory.
All
disk-control
commands
and
command-completion
reports
go
through
this
channel.
The
organization
of
these
structures
is:
Dispatch
Table:
15 o
+------------------------------------------------+
DT:
+
0:
PSO
(Drive
0
Packet
status)
:
+------------------------------------------------+
/ /
/ /
+------------------------------------------------+
61
PS3
(Drive
3
Packet
Status)
:
+------------------------------------------------+
8:
PACKET
0
ADDRESS
M.S.WORD
:
+------------------------------------------------+
A:
PACKET
0
ADDRESS
L.S.WORD :
+------------------------------------------------+
/ /
/
/
+------------------------------------------------+
14:
PACKET
3
ADDRESS
M.S.WORD
:
+------------------------------------------------+
16:
PACKET
3
ADDRESS
L.S.WORD :
+------------------------------------------------+
DT:F'Sn
Packet:
Packet
Status
for
packet
On:
o =
IDLE
(set
by
host)
1 =
GO
(set
by
host
when
packet
ready
to
go)
2 =
BUSY
(set
by
controller
after
packet
is
read)
3 =
DONE
(set
by
controller
after
packet
command
is
completed)
15 14 13 12
11
10 9 8 7 6 5 4 3 2 0
+--------------+--+--+--+-----------------------+
+ 0
CM:
I 0
---------0
lNRINElNOI
PCMD
(packet
command) :
+--------------+--+--+--+-----+-----------------+
2
ST::
0
------------------------0
lES(ending
status):
+-----------------------------+--------+--+--+--+
4
SB::
0
--------------------------------
0 IRZIRTlEC:
+----------+------------+--+--+--+--+--+--+--+--+
6
DS::
SKE
:
SEL
: x: xI
BZ
I
RO
I
FT
ISE:
OC
I
RY:
+----------+------------+--+--+--+--+--+--+--+--+
A-30
Zilog
A-30
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