Output Control Lines - Tandon TM848-1E User Manual

selects the Read/Write head on side zero, the
lower head of the drive. A true (low) level on
this line selects the Read/Write head on side
one, the upper head of the drive. When switch-
ing from one head to the other, a 100 micro-
second delay is required before any Read or
Write operation can be initiated.
HEAD LOAD LINE/MOTOR CONTROL
This line may be used to control the spindle
motor and/or the lever lock solenoid (see
Section 3.6).
OUTPUT CONTROL LINES
There are eight output lines, five of which are
standard and three of which are strappable
features. The standard output. signals are:
Index/Sector, Track 0, Write Protect, Read
Data, and Ready. The strappable output sig-
nals are Disk Change, Two-Sided, and True
Ready.
INDEX
The Index signal represents the output of the
Index sensor. An Index pulse is provided once
every revolution, 166.67 milliseconds nominal,
to indicate the beginning of a track to the
controller. The leading edge of this signal
must always be used to ensure timing
accuracy. The Index line remains in the true
(low) state for the duration of the Index pulse,
which is nominally four milliseconds.
TRACK 0
When the drive is selected, the Track 0 inter-
face signal indicates to the controller that the
Read/Write head is positioned on Track 0, the
outermost track. This signal remains true
(low) until the Read/Write head is moved
away from Track
o.
This signal is false (high)
when the selected drive's Read/Write head is
not on Track O.
3-5
WRITE PROTECT
The Write Protect signal is provided to indi-
cate to the user that a write protected diskette
is installed. This signal is true (low) when the
diskette's Write Protect notch is uncovered.
When the Write Protect signal is false (high),
the write electronics are enabled, and write
operations can be performed.
READ DATA
The Read Data line transmits data to the con-
troller when the drive is selected and not
writing. It provides a pulse for each flux tran-
sition recorded and detected on the diskette by
the drive electronics. Normally, this signal is
false (high). It becomes true (low) for the
active state. The Read Data output line goes
true (low) for a duration of 200 nanoseconds,
±
50 nanoseconds, for each change recorded
on the diskette.
READY
The Ready interface signal indicates a disk-
ette has been inserted into the drive. Ready
will not return to the false state until the
lever is opened, and is not affected by Spindle
Motor Control.
When a single-sided diskette is installed,
Ready is active (low) if side zero is selected.
Ready is false (high) if side one is selected on
the TM848-1E. When a two-sided diskette is
installed, Ready is active when either side of
the diskette is selected on the TM848-2E.
TRUE READY
The True Ready interface signal indicates the
diskette is rotating at 360 RPM, and a seek
operation is complete, Le., the head has
settled. This may be used to indicate seek com-
plete when using the buffered seek operation.