W Rite And Read Data - Tandon TM362 Manual

DRIVE SELECT - - - - -
HEAD SELECT - - - - . . . ,
3 MICROSECONDS ~I ~
MAXIMUM
r--
MFM VALID _ _ _ _ _ ---'
READ DATA
WRITE GATE - - - - - - - - - - - - ,
~I
50 NANOSECONDS
----'lIII0....1
~
TYPICAL --".--
1--
~I
L
3 MICROSECONDS
I
MAXIMUM
l- _
410 NANOSECONDS
~
MAXIMUM
MFM VALID
WRITE DATA
___________________
rLflJlJl~
____________ __
FIGURE 3-13
WRITE AND READ DATA TIMING
MFM WRITE DATA
This is a differential pair that defines the transitions
to be written on the track. When Write Gate is active
the transition of the signal
+
MFM Write Data go-
ing more positive than - MFM Write Data causes a
flux reversal to be recorded on the track. When Write
Gate is inactive the host system must hold
+
MFM
Write Data more negative than - MFM Write Data.
The standard MFM Write Data transmission rate is
5 megabits per second. The actual occurrence of flux
reversals may differ due to write precompensation.
WRITE PRECOMPENSATION
Tandon does not recommend write precompensation.
3-16
MFM READ DATA
The data recovered by reading a pre-recorded track
is transmitted to the host system via a differential pair
of MFM Read Data lines. The transition of the
+
MFM Read Data line going more positive than the
- MFM Read Data line represents a flux reversal on
the track of the selected head.
Read data is suppressed during writing operations and
when the drive is not selected. Following a write
operation and/or a Head Select change the read data
will not be valid for a period of up to 3 microseconds.
If the drive is already selected at the end of a seek
operation, read data will appear immediately upon
Seek Complete. When the drive has been deselected,
read data will not reappear for a period of up to 100
microseconds after it is reselected.