P
P
r
r
o
o
-
-
B
B
e
e
l
l
L
L
t
t
d
d
T
T
e
e
c
c
h
h
n
n
i
i
c
c
a
a
l
l
m
m
a
a
n
n
u
u
a
a
l
l
H
H
U
U
-
-
F
F
r
r
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e
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w
w
a
a
y
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R
R
a
a
n
n
g
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S
S
y
y
s
s
t
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m
m
U
U
s
s
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r
r
G
G
u
u
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d
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3
3
7
7
4
4
C
C
o
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n
n
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r
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l
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s
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m
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p
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r
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a
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n
n
The following sections describe the control system of
Freeway
. The control module
provides the interfaces, database and software to configure and control the
Freeway
series routers.
n
n
4
4
.
.
1
1
M
M
a
a
s
s
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t
e
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r
r
a
a
n
n
d
d
s
s
l
l
a
a
v
v
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m
m
o
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d
d
u
u
l
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d
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t
t
a
a
i
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s
s
The
Freeway
unit containing the plug-in control modules is designated MASTER and
all other units are designated SLAVES as they are slaved off the master using a
unidirectional parallel bus. Each of the main router units has level address select
switches that are used to identify each of the control levels.
Each router provides a module detect (handshake) mechanism so that the system
control module can detect the presence of various router units.
n
n
4
4
.
.
2
2
M
M
a
a
s
s
t
t
e
e
r
r
r
r
o
o
u
u
t
t
e
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r
r
d
d
u
u
a
a
l
l
c
c
o
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n
n
t
t
r
r
o
o
l
l
a
a
n
n
d
d
c
c
h
h
a
a
n
n
g
g
e
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o
o
v
v
e
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r
r
In a dual-control environment, one card is ‘ACTIVE’ while the other is ‘IDLE’. In the
event of the ‘ACTIVE’ controller failing, the ‘IDLE’ controller will take over control of
the frame and become ‘ACTIVE’.
On power up, the controller designated MASTER will also become ‘ACTIVE’. Every
main loop, the software checks whether a changeover has occurred. When a
controller changes state from ‘IDLE’ to ‘ACTIVE’, or on power-up, a message is issued
to General Remote ports to report this fact. Thereby this information may be relayed
to an external control system such as a Pro-Bel System 3 controller. An Editor’s
version message will also be displayed on the editor terminal.
Both controllers contain identical data concerning the state of the system. This is
maintained by incorporating a serial link between them. Tally information is
requested on a background basis by the idle card.
Arbitration ensures only the active card sets crosspoints.
If a second card containing a control module is plugged into a frame containing an
active controller, the database is automatically downloaded to the new (idle)
controller.
