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c. Data is entered into the Cyl 256 FF
and
Cyl 512
~when
controller drops
Serial Write OUt (Sample ttMe -
DC,l) •
d.
FF
Kl200 is set.
Refer to step
4
for
this function.
e.
Drive drops Serial Read
In
two
micro-
seconds after fall of Serial Write
Out.
4. Controller places bits
27
through
2
0 of
new address on bidirectional data lines.
Since new address is decimal 160, this
byte is 1010 0000.
Controller also
raises Cylinder Out Lower (Tag 07) and
Serial Write Out.
a. Drive decodes command.
b. Drive raises Serial Read In.
c. FP K1200 clears when controller drops
SHO.
If Cylinder Out Lower had pre-
ceded Cylinder Out Upper or if Cyl-
inder Out Upper were never issued,
this FF would set Invalid Command
Sequence (bit 24 of Detailed Status
Byte
~
(Tag 29) and raise DLI Fault.
Refer to Seek Status and Error Cond-
ditions for additional information.
d. At the same time (ce'l), contents of
bidirectional data lines plus the
Cyl 256 FF
and
Cyl 512 FF
*
are
loaded into drive's Cylinder Address
Register.
This reqister is auto-
matically reset to zero by an RTZS
function (Recalibrate or Device
Initialize) or First Seek.
e. Drive drops Serial Read In two micro-
seconds after fall of Serial Write
Out.
5.
Controller raises Head Address In Upper
(Tag 20) command.
a. Drive decodes command.
However, for
HIU, the output of the command decoder
has no outout.
Therefore, no data is
placed on bidirectional data lines
except for parity.
b.
Drive raises Serial Read In.
It drops
in response to Serial Write Out.
6.
Controller raises Head Address In Lower
(Tag
21)
command.
a. Drive decodes command.
b. Bits
24
through 2° of Head Register
are placed on bidirectional data
lines.
Bits
27
through
2 S
are auto-
matically zero.
*
Not applicable to
BR3E4/3ES.
3-56
c. Drive raises Serial Read In.
It
drops in response to Serial Write
Out.
d. There are no restrictions on Head
Address In Upper/Head Address In
Lower: they may be
in
any sequence
or omitted.
7.
Controller raises Head Address Out
~
(Tag
08)
command and raises Serial Write
Out.
a. Drive decodes command.
However, for
Head Address Out Upper the output of
the command decoder has no output.
Therefore, no data is accepted from
bidirectional data lines.
b. Drive raises Serial Read In then
drops it
two
microseconds after con-
trOller drops Serial Write Out.
8.
Controller places new head address on
bidirectional data lines and raises
Head Address Out Lower and Serial Write
Out.
a. Drive decodes command.
b. Drive raises Serial Read In.
Co
When contrOller drops Serial Write
Out (Sample time), drive performs
steps
d
and e.
d.
Bits
24
through
2
0 of bidirectional
data lines are loaded into Head
Register.
High-order bits, if any,
are ignored.
Head Register is auto-
matically reset to zero by either an
RTZS or First Seek function.
f. Drive drops Serial Read In two micro-
seconds after fall of Serial Write
Out.
9.
Controller computes difference between
current address (obtained from Tag 22
and
23)
and new address.
On a seek
from cylinder 10 to
160,
the difference
(tracks-to-go) is 150.
Controller also
determines if seek should be forward
or reverse.
10.
If difference is
256
or more cylinders
controller turns on bit
2 0
of bidirec-
tional data lines and will also turn
on bit
21
if difference is
512~or
more
cylinders.
In this case, the bit is
zero.
Controller also raises Seek
Forward Upper (Tag 02) and Serial Write
Out.
a. Drive decodes command.
b.
Drive raises Serial Read In.
83318200
C
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