Specifications

DC POWER
I ~ --------------~l~l---------------
DRIVE SELECT
I
DIRECTION SELECT ___ 1 ___ _
~
--1~1:1 .s
r--- -
I
------_ ....... ' -- --
OUT
~----------------
STEP
90
ms
MIN
LJlJ
1 /ls MIN~
r I 15"s MIN" .~
r-2.~ ms MAX
~ 15/l8 MIN**
I 2.9 ms MAX"
* After the last step pulse has been issued the drive may be deselected. The drive ignores any
change to the DIRECTION SELECT line when no further step pulses are received. This frees the
controller to issue instructions to other drives while the first drive completes the step commands
stored in the buffer.
* * Pulses received at less than a 3 ms period will be stored in a buffer which will then issue step com-
mands to the drive stepper motor at a 3 ms pulse rate. Pulses received at greater than a 3 ms per-
iod will step the drive at the same rate they are received. The first step begins upon receipt of the
first step pulse.
39216·31
FIGURE 1·4. TRACK ACCESS TIMING, BUFFERED SEEK
1.4.7 Side Selection (SA860 Only)
Head selection is controlled via the I/O signal line designated SIDE SELECT. A plus logic level on the SIDE
SELECT line selects the
read/write head on the side a surface of the diskette. A minus logic level selects the side 1
read/write head. When switching from one side to the other, a 100 JLS delay is required after SIDE SELECT
changes state before a read or write operation can be initiated. Figure 1-5 shows the use of SIDE SELECT prior to a
read operation.
DC POWER
DRIVE
SELECT
STEP
SIDE
SELECT
(SA860 ONLY)
WRITE
GATE
~~------------------------------~u~----------
I
'--------------------------------------------~l~~------------
.--------------------------------~l~~---------------
1-100 "s
-----------------------------~?~~-------------
VALID READ DATA ------------------
*Or when TRUE READY comes active.
39216-04
FIGURE 1·5. READ INITIATE TIMING
1-7