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7925
Troubleshooting
9
10
11
12
13
14
15
16
17
o
A
C
NOTE: All D-type flip-flops are
clocked on the rising edge
of the clock signal.
Mainframe Assembly. .. . . . . . . . . .. . . . . . . . . . .. 4-39
I/O Control System
4-41
Spindle Rotation System
4-43
Head Positioning System. . . . . . .. . . . . . . . . .. .. 4-45
Sector Sensing System. . . . . . . . .. . . . . . . .. .
4-47
Read/Write System
4-49
Fault Detection System
, 4-51
STA TUS/H EAD-SECTOR
MULTIPLEXER
12
NOTE:
STATUS IS OUTPUT UNLESS
RQP· SEL ARE ACTIVE.
STATUS
BIT 11
6
STATUS
'---+--+---BIT 10,
STATUS
- - - - - - t - + - - -
BIT 8
STATUS
- - - - - - + - - - - + -
BIT 5
1--+-_ _
2°
STATUS
.....-----e_--+-+---
BIT 9
W5
SEE {
DETE6~~6~
F L T - - - t - - - + - STATUS
SYSTEM
BIT 4
DIAGRAM
(C14)
RQS. SEL
DRIVE TYPE
(A4)
7920
0
00-011 - - - - - - - - - - - - - - - - - - - - - . - . - - - - - - - - - - - - - - - - - - - - -
I....-----SEEK CHECK
-+_ _ --+_S~~_i~S
. - - - - - - - - - FORMAT
al--------<:>---
'C
S
SEci~~{
SENSING
PRESENT
SYSTEM
- - - - - SECTOR
DIAGRAM
{
(B7)
READIWR~~~
ADDRESSED
DI~YGSri;~
- - -
HEAD
-----r--------. . . . . . . .
(D4)
~g~~
__
+-_ _
f--S~~;~S
POSITlO~~~g
{
DRDY _ _
-+-_ _
+-STA~US
SYSTEM
BIT
1
DIAGRAM
(B3)
2
1
' ) - - 3 - - - - - 1 0
ILLEGAL HEAD ADDRESS
(HEAD>
!l)
ILLEGAL SEC rOR ADDRESS
ISECTl'n
>
63)
ILLEGAL CYLINDER ADDRESS
(CYLINDEIl:- (22)
Ofl
MULTIPLE SEEK COMMANDS
FIRST
STATUS
Q
I--...:
F ...:. F
FIRST STATUS
- - - - - + - - - + _
S~~_i~S
COUNT
817
- - COMPARE - - -
PRESENT _ ADDRESSED
SECTOR -
SECTOR
POSITIO~~~g
{D:::
S
SYSTEM
DIAGRAM
(B3)
SEE
FAULT
DETECTION
SYSTEM
DIAGRAM
(B4
&
B5)
WRITE. SEL
(A4)
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - 1
I
I
I
I
I
I
\,
•
SEE
SECTOR SENSING
SYSTEMD lAG RAM
(C8)
CLS. SEL
(B4)
Dl
{
25
READNlR~~~
READ - - - + - - - - S T
B
A
IT
TU
6
S
D1~Y~ri;~
ONLY
(C4)
I....--+-------------------------------SE-C-T-O-R-----~-
ATTENTION - - - - - - t - - t - - -
S~~_i~S
READ. SEL
COMPARE
•
~
(A4)
FF
I
SECTOR
COMPARE
DO
J
J
CLS. SEt
(B4)
00
,
. - - - - ( : l - -.....
---I~
AT
(C3)
ACRY
(B15)
SEEK-ICA
ATTENTION
FF
Q
D
+5V
S
~----tC
00-010
SK
DO-D5 & D7
TO OFFSET
MAG,NITUDE
&SIGN
REGISTERS
SEE
HEAD POSITIONING
SYSTEM DIAGRAM
(Bl)
7,8,9,10,11,
-.J
F,H,K,L,M
_'
,_'-
I
_
10
DO-D9
P:j
L
SEL
SEE
FAULT
DETECTION
SYSTEM
DIAGRAM
(A3
&
B3)
SELECT
FF
Q
SEE
SECTOR
SENSING
SYSTEM
DIAGRAM
(BB
&
Bl0)
ADU
}
SEE
,
READ,wRITE
SYSTEM
DIAGRAM
(B3)
D8-Dl0
TO HEAD
ADDRESS
REGISTER
DCN
NDPS
(B13)
._-----::lr'-----.
~g-~~CTOR}
ADDRESS
REGISTER
COMPARE
- - - - - - t - - - - - - I
}
SEE
READ,wRITE
(C3
&
04)
, &
SECTOR SENSIN, G
(C7
&
C9)
SYSTEM DIAGRAMS
D2
01
CLS. SEL
(B13 & B14)
DO
US2
,USO
RQI (A4)
AT{B13)
RCL. SEL
}
SEE HEAD POSITIONING
t-------....
(C12)
~~~~ ~:S~~~T~~~~~~~N
}
SEE SECTOR SENSING
XMS. SEL
(B8) & FAULT DETECTION
(B3) SYSTEM DIAGRAMS
t-------....
-SOF
- - - - , - - - - - - - - - ~ - ~ - - - - -
__
- - - - ~
1--
....
Rap • SEL
(D3
& C16)
1 - - - - - - -....
~D~S;~lE5~
- - + - - - - - - - - - - - - - - 4 . - r~~
. . . - - - - - - - - - -...... READ
READ. SEL
1 - - - - - - - - 1 . (D3 & C14)
r------I.
WRITE
--t-----~....._t
WRITE. SEL
(03 & C14)
SEE HEAD POSITIONING
SEEK. SEL
}
(Bll & FAULT DETECTION
(C12 & B12)
(A4) SYSTEM DIAGRAMS
~
SEE SECTOR SENSING (BB) & FAULT
I - - - - - - -....
ADR • SEL
DETECTION (B3) & READ/WRITE (C3)
SYSTEM DIAGRAMS
--+------------..-
A D U - - - - - - - - - - - - - - - 1 I - - - - - ,
SEEK
READ
WRITE
REQUEST
STATUS
ADDRESS
RECORD
ADDRESS
UNIT
REQUEST
iDENTITY
REQUEST
SECTOR
ECALIBRAT
TRANSMIT
SECTOR
SET
OFFSET
CLEAR
STATUS
O I S C O N N E C T - - t - - - - - - - - - - -....-
D C N - - - - - - - - - - - - - - - ,
CO~~~~iiER--+-----------
.....-
CPS
- - - - - - - - - - - - - - 1 - - - - 1
t-------------l - - -
S E L - - - - - - - - - - - - - - - - - - - - - - + - - - + - - - - - - -....- - - - - - -. .
TAG
BUS
DECODER
+5V
Jl
I
P/O
I/' O SECTciR' P cA.A2" - - - - - - - - - - - - - - --- --- --- - - -- --- -- - - --- --- --- --- --- --- --- --- --
--p0
}
~~~LT
L
) > - - - - - - - - - -
CPS
••
~~~~~~ION
I
~~GRAM
,.....--
Pl~
f)
SOF -
}
P2
I
}
~~~D/WR
ITE
r-----~
8
>--
SEL
~
~i;~~~M
(C5)
TBUSO-3~
37,39,
41,43
I
'STB
I
10
1
STB
~
1
>--'-_~'D-
__
1.--<lI
STROBE
SEL,
--<
1
1
3
,Pl'
I
I
I
FROM
CONTROLLER
I
P2
- - - - - - USO
- <
A
~.--+-
__
t__-..,...-------~:........-~--~:........---_
I
- - - - - - US1
-<
1
I
- - - - - - US2
- <
17 t--
P
_
1
_ _......_
I
I
I
I
I
SEd6~t
I
SENSING
(PRESENT
LOOK
=
ADDRESSED)-o
SYSTEM
SECTOR
+
AHEAD
SECTOR
DIAGRAM
I
(A9)....
....
---c€
READ. SEL (A4)
~~l~i~
~:ES~~~~~41
I
RQP. SEL (B41.
7/
1 2 )
):J..:,.l
-...c------t--<
3,4,5,6,7,8,9,
I
10,21,23,25,27
L
J
TO/FROM
{
CONTROLLER
[' N 0oooiiPCA-Ai11
I
J
I
~DECIMAL
I
POINT
UNIT
I
I
SELECT
DISPLAY
A
B:
15
16
17
~
l'
tj
UNIT
C
SELECT
SWITCH-S3
7311-260
I
7
11,
12
13
14
15
f6
17
Figure 4-24. I/O Control System, Functional Diagram
4·41/4·42
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