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1.3.13 MICROPROCESSOR CIRCUITS
The Q2080 uses an 8031 microprocessor to control the drive during operation. The microprocessor interfaces
are shown in Figure 1-35.
STEP
-R
ESET
+0 I R IN
,
4
u6G
T0
Pl.o
/
SEL LINES
INTi
PI.3
....
STEP
ONE
.....1!!2L
8
~
P2.0
U3H
CONTROL
+SEEKMODE
-INDEX~
+TRACK 0
INa
BIT
+RST PEAK OET
J..
UJH
~
SEEK
COMP
LATCH
.I
r - - -
u6H
01 R
LATCH
'-->
A/v IN
LATCH
8031
+READY
MICROPROCESSOR
+ENA DVR
I
RD
_+SEEK
COMP
4
ADDRESS
l1
ALE
UJG
U5G
ADDRESS
ROM
/
DATA
BU~
LATCH
AOiiRi
15--"':::'
N
I'
iE
-
•
PI.5
PSEN
sV
DATA
,
i
11
iii<
AD
iG
IT
v
IT
U7G
8
U8F
U2G
O/A
/
D/A
AID
LATCH
nGURE 1-35
MICROPROCESSOR CIRCUITS BLOCK DIAGRAM
-
-
TO
ACTUATOR
The STEP ONE-SHOT (U6G) separates STEP pulses slower than a nominal 535
,,",S
and interrupts (INTl) the
microprocessor every time STEP pulses go slower than 535
,,",S.
U6G is a retriggerable one shot with timing equal to
.45 (RUl) (C50)
=
535
,,",S.
The SEEK COMPLETE LATCH (U3H) clocks in SEEK NOT COMPLETE when STEP pulses begin. The
microprocessor sets SEEK COMPLETE when the seek is finished. U3H is a D-type flip-flop.
The DIRECTION LATCH (U6H) clocks the direction bit into the microprocessor.
It
is a D-type flip-flop.
In order to read the main program stored in EPROM U5G-2732 4K x 8, the microprocessor sends ADDRESS
via P0 (data bus) and P2 (lower 4 bits). U3G latches the ADDRESS during ALE (address latch enable). The 2732
puts the data to
Of)
to 07 and PSEN (program store enable) goes LO enabling 00 to 07 onto the data bus.
The CONTROL BIT LATCH (U5H) holds the control bits until the microprocessor issues a READ command.
This latch is required because the microprocessor uses P2 for both ADDRESS lines and control bits. -RESET starts
the control bits in the right state. U5H is a 74LS 273 octal latch.
1.3.14 INDEX GENERATION
The Q2080 uses a metal index ring on the disk mounting hub below the bottom disk to generate index signals.
The ring has 55 index slots and one of the slots has an extra rib dividing it into two smaller slots. The two smaller
slots signal the once-around index. A magnetic transducer picks up signals as the slots rotate past and sends these
signals to the index comparator (LM311) that squares the waves at the zero crossings. The signal then goes to the
RESET one-shot, which resets the microprocessor when disk speed is less than 2000 RPM. The index comparator
also sends a signal to the once-around separator, which separates the extra once-around pulse from the 54 INDEX
pulses. The block diagram in Figure 1-36 illustrates the index generation circuit.
REV A (01/84)
1-32
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