Note: Descriptions are shown in the official language in which they were submitted.
The invention relates generally to a control sys~em for an
automated work station and rnore particularly to a three-~la~ data
communication switch for interconnecting a hos~ computer and an operator
terminal to the work station controllerO
Robots are increasingly used in the manufacture of
electronic equipment, particularly the electronic component assemb~y of
printed circuit boards. Such a robot usually comprise a small special
purpose computer or controller and a control terminal. The controller
memory may be loaded with instructions defining the tasks to be
accomplished by the robot. An operator terminal is connected to the
communications port of the controller and is used to alter and/or add to
the instructions in the controller rnemory.
It is very advantageous to be able to use a robot in
cornbination with a CAD/CAM system (computer-aided design/computer-aided
manufacturing). A CAD system is capable of capturing and formalizing a
design from a designer. In the case of a printed circuit board, this is
followed by automatic component placement and connection routing then
generation of manufacturing data such as photo-mask and drill tape. To
support this process, a CAD system has a comprehensive database in which
the location of all the components on a printed circuit board are stored
and this information rnay be supplied to a robot For its assembly task.
The host computer which runs the CAD system can be
configured to drive a robot by composing robot programs each consisting of
a series of discrete movernents and then load them into the robot's program
rnernory, In addition, a host computer linked to a network of robots could
perForm a variety of supervisory and backup functions such as robot task
archiving and dispatching, cold start and bootstrapping, process control
and synchronization, inventory control, and statistics gatherin~
As mentioned abovel a robot system controller comes equipped
with a transmission port, usually using the EIA RS-232C transmission
standard, for connection to a control terminal. However, there is often
no provision for a second transmission port to which the host compu~er of
a CAD system could be connected. Therefore, it is an object of this
invention to provide a device which may be inserted into an exis~ing data
transmission link to create in effect a second input transmission port to
the robot controller thereby to permit its connection to both the CAD
system host computer and an operator terminal.
In accordance with the invention, there is provided a
three-way switch adapted to be inserted into a data transmission line.
The switch comprises a first bidirectional port for connection to the
communication port of a first computer via a first portion of the
transmission line, a second bidirectional port for connection to the
cornmunication port of a second computer via a second portion of the
transmission line, and a third bidirectional port for connection to an
operator terminal, said switch having logical circuitry operable under
control of a switch means, for interconnecting any pair of the three
bidirectional ports.
Basically, the invention provides a simple and economical
switching device which, when inserted into a transmission line, provides
an additional switched bidirectional port thereto as well as a selectable
monitoring capability.
An example embodiment of the invention will now be described
in conjunction with the drawings in which:
Figure 1 is a block diagram showing a control system for an
automated work station including a three~ ay switching device, in
accordance with the invention; and
Figure 2 which is a logic schematic diagram of the switçhing
device of figure 1.
Figure 1 illustrates a three-way switching device 10 having
a first bidirectional port HR-HT connected to a host computer 11 via a
first portion of transmission line 12. The computer 11 may be any one of
a large variety of commercial units as for example model DEC-20 from
Digital Equipment Corporation. The device 10 has a second bidirectional
port CT-CR connected to the T port of a robot controller 13 via a second
portion of transmission line 12. The T port of controller 13 normally
supports the connection of an operator terminal such as 15 which may for
example be a Regent Model 20 manufactured by Applied Digital Data Systems,
Inc. The device 10 has a third bidirectional port TR-TT for connection to
terminal 15. The robot controller 13 provides control signals to a robot
14 and together they comprise a commercial product available off-the-shelf
and may for example consist of a robot model 560 manufac-tured by Unimation
Inc. of Danbury, Connecticut. Transmission line 12 is one that meets the
2n requirements of EIA Standard RS-232C.
The device 10 may be inserted anywhere along the length of
transmission line 12 and, as discussed below, may be switched to become
transparent thereto. The device 10 thus effectively provides a second
transmission dal;a port for the robot controller 13, allowing the
connection of operator terminal 15 thereto. The terminal 15 may act as a
data entry terminal to either the host computer 11 or the robot controller
13 or it may act simply as a monitor for the data transmitted between
thern.
Figure 2 is a logic schematic diagram o-f the device 10. The
data appearing on terminals TT, c-r, and HT appear at interface circuits
20, 21, and 22 which act as level translators for the data frorn units 1l,
13, and 15 to the level of the logic gates of switching device 10.
Similarly the -transmit interface circuits 23, 24, and 25 act as level
translators and data drivers to their respective units 11, 13, and 15 from
the switching device 10. The receive and transrnit circuits may be
off-the-shelf circuits as for example Texas Instruments type SN75154
(receiver) and type SN75150 (driver). The AND gates 26 - 31 and OR gates
lU 32 - 36 may be any suitable off-the-shelf components. The mode selector
circuit 37 may conveniently be a Texas Instrument type SN74LS138 de oder
circuit which responds to a combination of input levels to provide a HIGH
enable signal on one of leads CTE, CHE, or HTE; with switch SW1 in
position 2, lead CHE is HIGH; with switch SW1 in position 3, lead HTE is
HIGH. Of course, the functions of the mode selector circuit 37 could also
be achieved through the use of a multiple contact, 3-position switch.
The Functions of the switching device 10 may be best
understood by reference to a description of its operation.
With switch SW1 in position 1, lead CTE is at a HIGH level
and yates 26 and 28 are enabled. The data transmitted by the operator
terrninal 15 appears on terrninal TT and is fed to the robot controller 13
via interface circuit 20, gates 26 and 33, and interface circuit 24 to
terminal CR. Similarly, the data transmitted from the controller 13 is
received at the operator terminal 15 via terminal CT, circuit 21, gates
28, 32, and 35~ circuit 23 and terminal TR. Therefore, with the mode
selector switch in position 1, an operator is able to communicate with the
robot controller 13.
With the switch SW1 in position 3, lead HTE is HIGH and
gates 27 and 30 are enabled. The data transrnitted by the operator
terminal 15 is routed to the computer 11 via the circuit 20, gates 27 and
34, interface circuit 25, and terminal HR. Similarly, the data
transrnitted by the computer 11 is routed to the operator terrninal 15 via
circuit 22, gates 30, 32, and 35, interface circuit 23, and terminal TR.
Hence, with the mode selector switch SW1 in position 3, an operator can
access the host computer 11 directly.
With the switch SW1 at position 2, lead CHE is HIGH and
gates 29 and 31 are enabled. The data transmitted by the robot controller
13 is routed to the computer 11 via the receive interface circuit 21,
gates 29 and 34, circuit 25, and terminal HR. Similarly, the data
transmitted by the host computer 11 is routed to the controller 13 via the
interface circuit 22, gates 31 and 33, circuit 24, and terminal CR. Thus,
with switch SW1 in position 2, the computer 11 is connected to the
controller 13 and the switching device 10 is transparent to the
connection.
When the mode switch SW1 is in position 2, the terminal 15
may be used as a monitoring device to "listen in" on the communications
between the cornputer 11 and the controller 13. With switch S'.12 operated,
the data from the controller 13 is fed from the output of gate 29 through
gates 36 and 35, and circuit 23 to the terminal 150 With switch SW3
operated, the data from the computer 11 is fed from the output of gate 31
through gates 36 and 35 and circuit 23 to the monitor terminal 15.
The invention provides a simple and economical data switch
which rnay be inserted in the communication path between two data
transceivers to provide for the connection of a third terminal. The mode
setting of the switch rnay be selected to allow the terrninal to become
interactive with either of the compui;ers or to simply serve as a
monitoring device for the cornlnunications between them. It is envisaged
that the host computer-monitor terminal combination could he used to
control a plurality of work stations by simply switching the terminals
CT-CR to any of the work stations.
