Data Transfer; Data Transfer Line Driver - Tandy 2000 Service Manual

READY
When true, the Ready signal, together
with
Seek
Complete, indicates that the drive is ready to
read,
write or
seek,
and the
I/O
signals
are
valid.
When
this line is false, all
controller-initiated functions
are inhibited.
The typical time after power on for
Ready
to
be
true is fifteen
seconds.
Track
0,
Seek Complete,
and
Ready
come true sequentially during power on.
SELECT STATUS
A
Status
line is provided at the JL/PZ connector to
inform
the host
system
of
the
selection status
of
the
drive.
The Drive
Selected
line
is
driven by
a
TTL
open col-
20
FT
lector drive
(see
Figure 3-7\. This signal goes
active
only
when the drive is programmed
as
Drive
X, X
_
0,
I
, 2, or 3, by progrilmming the shunt on
the
drive, and the Drive
Select
X
line at
Jl/Pl
is
ac-
tivated by the host
system.
DATA TRANSFER SIGNALS
All
lines associated
with the
transfer
of
data
be-
tween the drive and the host
system are
differential
in
nature and may be multiplexed. These lines
are
provided
at
the
JL/PZ connector
on all
drives.
Signal levels
are defined by RS422A.
Two pairs
of
balanced lines are used
for
the
transfer
of
data:
MFM Write
Data and
MFM
Read
Data. Figure
3-
10 illustrates
the
driver
/receiver
combination
used
with the drive for
data transfer
signals.
HIGH
TRUE
E
MAXTMUM
__t
(6
1M)
|
FLAr
RTBBON
OR
I
TWISTED PAIR
CABLE
I
HIGH
TRU
E
FIGURE
3.10
DATA TRANSFER LINE DRIVER
RECEIVER
+
SIG
NAL
SIG
NAL
{
?
I
100(J
261S3 1
0R
EOUIVALENT
261532
0R
EOUIVALENT
3- 13