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MNEMONIC
DSO-L
DSIN-L/
DSOUT-L
DX,DY
EOI-L
GREEN-L
HSO-L,
HSI-L,
HS4-L, HS8-L
HSI-H,
HS2-H
IFC-L
INDX-L
Theory of Operation
7942 and 7946
Table 3-1. List of Mnemonics (Continued)
SIGNAL
Drive Select, bit
o
Data Strobe In/
Data Strobe Out
Diff eren tial
Data
End Or Identify
Green
Head Select, Bits
o
thru 8
Head Select, Bits
1, 2
In terf ace Clear
Index
SOURCE
A2
III
AS
-
Al
III
AS
-
A2
III
A2
III
Al
III
AS
-
Al
III
DESCRIPTION
When
active
(low),
connects
the
ST-506 Interface control lines to
disc drive assembly A 1 interface cir-
cuitry. Output to disc drive assembly
A 1
III
via cable W 3.
DC-IB HDC-generated strobe lines
which accomplish the transferring of
data between the the HDC and one or
two DDC's over Read/Write Data Bus
DATAO-H through DATA 7-H.
Differential signal lines to/from read
preamplifier/write driver IC's.
HP - IB control signal used to indicate
the end of multiple byte transfers or
used with signal A TN - L to perform a
parallel polling sequence.
Dri ve for green LED in f ron t panel
FAULT/ON LINE indicator. Output
to the front panel via cable W 4.
ST- 506
Interface
control
signals.
These lines provide a means of select-
ing each individual read/write head
in a binary -coded fashion. When all
four lines are inactive, head 0 is selec-
ted.
Output to disc drive assembly
A 1
III
via cable W 3.
Head
select
bits
input
to
read
preamp/write driver IC's from the
head select and control logic.
HP - IB general management line used
to place the interface system in a
known q uiescen t state.
ST- 506
Interface
control
line.
INDX -L is provided by disc drive as-
sembly A 1 once each revolution of
the disc (16.67 milliseconds nominal)
to indicate the beginning of a track.
3-25
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