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4.5.3
A-cable input signals
(1)
Unit Select Tag
This signal gates Uni t Select 1,2 and 4 to select the drive. Refer to timing
of Uni t Select (Figure 4.5.9 if dual channel option is not installed. or Figure
4.5.29 if dual channel option is installed) . Elabora tion
0
f the dual channel
select operation follows.
Suppose that the dual channel option is installed and the drive has been
reserved by Unit Select command from channel-A, the drive is not
selectable from channel-B until a Release command will be issued from
channel-A or the internal 500 ms re-trigger timer times out.
However,
Priority Select from channel-B can interrupt the reserved status at any
time.
(Refer to Figure 4.5.29)
On the other hand, if the dual channel option is installed and the drive
has been reserved by a Priority Select command from channel-A, channel-B
cannot reserve the drive with Unit Select or Priority Select command until
a Release command from channel-A is issued.
(Refer to Figure 4.5.30)
(2)
Unit Select 1, 2 and 4
These three signals are binary-coded to select the drive and are validated
by the leading edge of Unit Select Tag.
The logical number of the drive
(0 through 7) is selectable by means of a switch located on the PCB
(B17B-0270-0010AHU).
Table 4.5.1
Tag/Bus
Bus
Tag 1
Tag 2
Tag 3
(With Unit
Cylinder Address
Head Address
Control Select
Select Tag)
0
1
1
Write Gate
-
1
2
2
Read Gate
-
2
4
4
Servo Offset Plus
-
3
8
8
Servo Offset Minus
-
4
16
16
Fault Clear
-
5
32
-
AM Enable
-
6
64
-
RTZ
-
7
128
-
-
-
8
256
-
-
-
9
512
-
Release*
Priority Select*
* Dual Channel only.
B03P-4825-0002A ... OlA
4 - 25
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Troubleshooting
