Note: Descriptions are shown in the official language in which they were submitted.
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POINT-OF-SALE SYSTEM AND DISTRIBUTED -
COMPUTER NETWORK FOR SAME
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates generally to computer networks and more
specifically relates to a distributed computer network suitable for use with a
point-of-sale system.
Descri~~tion of the Prior Art
In a point-of-sale system, a plurality of peripherals, such as cash registers,
displays, credit card readers, bar code scanners and the like, need to
communicate with a computer server which controls the data processing
operations for the system in which these peripherals operate. While computer
networks are known for use in point-of-sale systems, these computer networks
typically employ standard computer components at each node in the point-of-
sale system (see Figure 1). These systems further include a complex and costly
server and hardware which employs a software network communications
management system to control communications with each node in the system.
Additionally, each node typically requires matching network communications
software and hardware which further increases the cost of the system. This
network topology, which is conventional to a standard computer data network,
results in severe cost and processing overheads which burden a point-of sale
system.
In a conventional personal computer (PC)-based point-of sale system, the
number of standard input/output (I/O) ports available to accept the numerous
peripheral components that may be required is clearly limited. Currently,
there
exist various configurations used to overcome the I/O shortage problems.
However, these schemes typically require the addition of dedicated hardware,
such as special port concentrator units or PC cards. These hardware additions
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not only increase the overall system _cost but they also burden software
developers, who must write special application software to address the added
non-standard I/O ports without causing data contention problems created by the
duplicate usage of I/O addresses and interrupt request (IRQ) numbers.
An additional problem associated with prior art point-of sale systems is
that, generally, different peripheral devices have different interface
requirements.
Thus, while one peripheral device may be directly connected to the computer,
other devices may require a separate interface box to convert its output data
to
a format that is compatible with the computer. Furthermore, each input device
requires a unique software identification number and interrupt for the
computer
to communicate with the device. This results in higher hardware costs and more
physical space for each peripheral device added to the system.
Accordingly, there remains a need in the fields of point-of-sale systems
and others for an alternative computer network tailored to the particular
requirements of a network system.
It is, therefore, a goal of the present invention to provide an improved
distributed computer network adapted for use with a network system.
It is another goal of the present invention to provide a distributed
computer network that allows the connection of multiple peripheral devices
with
the limited number of input/output ports available.
It is yet another goal of the present invention to provide a distributed
computer network that allows the connection of additional peripheral devices
without shutting down the computer or reconfiguring the software, thereby
reducing system down-time.
It is a further purpose of the present invention to provide a distributed
computer network that eliminates the need for special hardware and/or software
drivers for peripheral devices, thereby allowing more flexibility in component
selection.
It is still a further purpose of the present invention to provide a
distributed
computer network that allows freedom of physical component placement.
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SUMMARY OF THE INVENTION
The foregoing needs, purposes and goals are satisfied in accordance with
the present invention, which, in one embodiment provides a distributed
computer
network for use with a general purpose computer having a communications port
and capable of running applications software for controlling the network. The
distributed computer network includes a master controller having first and
second communications ports, the first communications port of the master
controller for operatively communicating with a general purpose computer.
The distributed network further includes one or more input/output (I/O)
controllers, each having a first communications port for operatively
communicating with the master controller and a second communications port
for serially communicating with one or more peripheral devices. The peripheral
devices are connected together in a serial daisy chain configuration. The
master
controller communicates with the input/output controllers via a multidrop RS-
485
network bus. The master controller also communicates with the general purpose
computer via a RS-232 serial bus, so that the master controller performs
protocol
management functions including conversion between RS-232 and RS-485
protocol, error correction and detection, bus arbitration and data buffering.
Preferably, the network includes a general purpose computer having a
serial communications port. The computer is capable of running applications
software for controlling a point-of-sale system. Each I/O controller unit
preferably includes a limited number of peripheral device interface ports, to
which one or more point-of-sale peripheral devices are operatively connected.
According to the present invention, each I/O controller is capable of
supporting a plurality of peripheral devices interconnected by a serial daisy
chain
expansion technique which allows peripheral devices to be freely integrated
with
or removed from the system without the need for reconfiguring or rebooting the
system. Each input peripheral device preferably includes an electronic
interface,
operatively connecting the input device to the serial peripheral device bus,
which
converts the serial data format of a particular input device into a data
format
compatible with the I/O controller. The interface monitors the peripheral
device
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bus to determine when the bus is available for transmitting data and is able
to
selectively disconnect input devices from the bus that are located further
away
from the I/O controller (i.e., downstream).
In one embodiment, the present invention is configured as a Kitchen
System. In the Kitchen System embodiment, one or more input/output
controllers include an indicating device, such as a buzzer, or a visual or
tactile
indicating device. The I/O controller also includes a display, such as a video
monitor. The I/O controller's input/output peripheral device is preferably a
bump
bar.
These and other purposes, goals and advantages of the present invention
will become apparent from the following detailed description of illustrative
embodiments thereof, which is to be read in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a block diagram of a PC based computer network known in the
prior art.
Figure 2 is a block diagram of a distributed computer network topology
formed in accordance with the present invention.
Figure 3 is a block diagram of a master controller formed in accordance
with the present invention.
Figure 4 is an electrical schematic diagram of an exemplary master
controller circuit, formed in accordance with the present invention and
depicted
by the block diagram of Figure 3.
Figure 5 is a block diagram of an input/output controller formed in
accordance with the present invention.
Figure 6 is an electrical schematic diagram of an exemplary input/output
controller circuit, formed in accordance with the present invention and
depicted
by the block diagram of Figure 5.
Figure 7 is a block diagram of one embodiment of a point-of-sale system
formed in accordance with the present invention.
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Figure 8 is a block diagram of a point-of-sale peripheral device
interconnection arrangement known in the prior art.
Figure 9 is a block diagram of a point-of-sale peripheral device
interconnection topology formed in accordance with the present invention.
Figure 10 is a block diagram of a wedge interface device, formed in
accordance with the present invention, internally integrated with a point-of-
sale
input peripheral device.
Figure 11 is an electrical schematic diagram of an exemplary wedge
interface circuit, formed in accordance with the present invention and
depicted
by the block diagram of Figure 8.
Figure 12 is a diagram illustrating one example of an I/O controller node,
including an I/O controller and related point-of-safe peripheral devices,
formed
in accordance with the present invention.
DETAILED DESCRIPTIQN OF THE PREFERRED EMBODIMENTS
Figure 1 represents a typical prior art distributed computer network having
a plurality of personal computer (PC) stations directly connected via a common
data bus to a personal computer network server. The disadvantages associated
with this topology have been discussed above. Figure 2 generally illustrates a
block diagram of a distributed computer network formed in accordance with the
present invention. Referring to Figure 2, the computer network includes a
conventional computer network server 2 which is capable of running
applications
software for overall control of the point-of-sale system. The server 2
preferably
takes the form of a conventional personal computer, such as that manufactured
by IBM or an equivalent thereof. The server 2 communicates with the
distributed
computer network via a serial communications port, preferably an RS-232 port,
integrated with the server 2.
The distributed computer network of the present invention further includes
a master controller 4, preferably hardware based. The master controller 4
functions as an interface node for the distributed computer network,
communicating with the server 2 and receiving instructions therefrom.
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Preferably, the master controller 4 is interfaced to the server 2 via an RS-
232
communications link. The master controller 4 preferably converts the received
serial communications from the server 2 into a multipoint communications
protocol, which is also referred to as multidrop communications protocol;
preferably an RS-485 protocol, for distribution along the network. As an
alternative, other serial communication formats known by those skilled in the
art
may be employed and the master controller 4 will perform the conversion from
the serial protocol used to communicate with the server 2 to the protocol used
to communicate with the other nodes of the computer network.
The master controller 4 further performs protocol management functions
including error detection/correction, data bus arbitration, data buffering,
and
hardware peripheral driver. By employing these functions in the master
controller 4, rather than in the server 2, the server 2 is liberated from
performing
burdensome communications network control tasks and can therefore operate
in a faster, more efficient manner. Using this approach in an RS-485 system,
for example, serial data communications or higher data rates of 115,200 baud
or higher can be achieved.
Referring to the block diagram of Figure 3, a preferred embodiment of the
master controller 4 is shown including a master control processor 8, a server
communications port 10 and a network communications port 12. The master
control processor 8 performs the bulk of the protocol management tasks
described above, including control of data traffic between the server
communications port 10 and the network communications port 12. The server
communications port 10 provides an interface between the server 2 and the
master control processor 8. As previously discussed, the server communications
port 10 preferably exchanges data with the server 2 via a serial RS-232 link,
although other similar data communications protocols are contemplated. The
network communications port 12 similarly provides an interface between the
master control processor 8 and the multidrop network, preferably an RS-485
bus.
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An exemplary master controller circuit 4, formed in accordance with the
present invention, is illustrated in the electrical schematic diagram of
Figure 4.
The circuit includes a microprocessor 14 which, together with a programmable
read-only memory (PROM) 18, a random access memory (RAM) 16 and related
peripheral components, functions as the master control processor 8.
Preferably,
the PROM 18 is a 512K electrically erasable PROM (EEPROM), such as
industry part number 29EE512 or equivalent, and is operatively connected to
the
microprocessor 14 via common address and data buses.
The EEPROM 18 stores the application program instructions to be
executed by the microprocessor 14 and is preferably field programmable to
facilitate system updates. Additionally, the RAM module 16 is preferably a
256K
static RAM, such as Sony part number CXK58257AM or equivalent, and is
preferably connected to the microprocessor 14 in a similar manner for
providing
data storage and retrieval space. It will be clear to those skilled in the art
that a
number of microprocessor circuits and architectures which are suitable for use
with the present invention may be employed and are generally well known. For
example, the text Microprocessors and Microprocessor-Based Syrstem Design,
by Mohamed Rafiquzzaman (CRC Press, 1990) provides a detailed discussion
of various microprocessor circuits and topologies.
The master controller circuit 4 further includes a serial RS-232 transceiver
20, such as Maxim Products part number MAX232 or equivalent, functioning as
the server communications port 10 of the master controller unit. The RS-232
transceiver 20 is operatively connected to the microprocessor 14 and provides
a data transfer interface between the server and the microprocessor 14.
Additionally, a multidrop RS-485 transceiver 22, such as Maxim Products part
number MAX491 E or equivalent, functions as the network communications port
12 of the master controller unit. The RS-485 transceiver 22 is similarly
connected to the microprocessor 14 and provides an interface between the
multidrop network bus and the microprocessor 14.
Preferably, the master controller circuit 4 includes an internal power
supply 21. The power supply 21 preferably provides a source of regulated DC
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voltage, suitable to meet the requirements of the master controller circuit 4.
It
is additionally contemplated that the power supply 21 may supply power to
other
system components that are connected to one of the communications ports 10,
12 of the master controller 4, thus reducing the number of external power
supplies required.
Referring again to Figure 2, the distributed computer network of the
present invention further includes one or more input/output (I/O) controller
nodes
6. Preferably, the I/O controller nodes 6 are interconnected through a
multidrop
RS-485 communications connection with data inputs and data outputs
interconnected to form a serial chain. As an alternative, other network
topologies, which are known in the prior art, may also be employed to provide
data interconnection between each of the I/O controller nodes 6 and the master
controller 4.
Referring to the block diagram of Figure 5, a preferred embodiment of an
I/O controller 6 formed in accordance with the present invention is
illustrated.
The 1/O controller 6 preferably performs local network management functions,
including receiving and transmitting data between the multidrop network bus
and
the peripheral devices) and translation of commands originating from the
application software to peripheral device controls.
Preferably, the I/O controller 6 includes a hardware interface 32 for
communicating with the RS-485 bus. The I/O controller 6 further includes an
input/output (I/O) node processor 30 for controlling the functions of the I/O
controller 6. Preferably, the I/O controller 6 includes limited peripheral
device
interfaces, including a keyboard interface 24, a video display interface 26
and a
serial communications !/O interface 28. The I/O node processor 30 preferably
communicates with the point-of-sale peripheral devices previously described
through the serial I/O interface 28 and/or keyboard interface 24.
Additionally, the
I/O controller preferably includes an indicator 31. The indicator 31 may be a
visual device (e.g., a light), an audible device (e.g., a bell or buzzer), or
a tactile
device (e.g., a vibrating element), for indicating that the I/O controller has
received data from the master controller.
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Since the point-of-sale peripherals include integral processing to control
their own functions, the I/O node processor 30 of the I/O controller 6 need
only
contain enough processing capability to perform network interface functions
and
peripheral communications control functions. This significantly reduces the
processing burden on the IIO node processor 30 and allows simplification in
the
design of these components.
An exemplary I/O controller circuit, formed in accordance with the present
invention, is illustrated in the electrical schematic diagram of Figure 6. It
is to be
appreciated that suitable IIO controller circuits for use with the present
invention
are well known by those skilled in the art and, therefore, an in-depth
discussion
of the IIO controller circuit will not be presented here.
One embodiment of a point-of-sale system formed in accordance with the
present invention is shown in Figure fi. This system is virtually identical to
the
system shown in Figure 2, except that each I/O controller 6 is shown having a
I S point-of sale peripheral device 7 attached thereto. An example of the
point-of-
sale system of Figure 6, adapted for use in a restaurant or similar food
establishment, is currently being commercially sold by IBM under the product
name "IBM Kitchen System."
The Kitchen System is a completely open system that attaches easily to
any PC-based computer using an RS-232 port. Included in the IBM Kitchen
System is a master controller and one or more I/O units. Attached to each I/O
unit is a "bump bar," preferably connected directly to a keyboard port of the
I/O
unit. The bump bar serves as a special keyboard device capable of providing
the codes to move ("bump") items previously displayed on a video monitor. The
video monitor, preferably a VGA or Super VGA monitor or equivalent, is
connected directly to the video port of the I/O unit. The Kitchen System
preferably supports up to sixteen I/O units, with each I/O unit supporting a
bump
bar and a video monitor. Additionally, an external power supply may be
provided
to meet the power requirements of the point-of sale system. Firmware
controlling the operation of the I/O unit is preferably field programmable, to
facilitate system updates and provide enhanced system flexibility.
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In a preferred embodiment of the present invention, each I/O controller is
preferably capable of supporting a plurality of point-of-sale peripheral
devices by
employing the communications and peripheral expansion technique illustrated
and described in U.S. Patent Application Serial No. 08/011,461 (now
abandoned), filed on January 26, 1993 by the same inventor as in the present
application. This prior application is incorporated herein by reference.
Referring now to Figure 7, there is shown a prior art system for
interconnecting point-of-sale peripherals to a personal computer (PC) station
(see Figure 1). Using this technique, a separate interface card is required
for
each peripheral device. Thus, the number of devices that a particular PC
station
can support is limited by the number of slots available within the PC station
to
receive interface cards. Furthermore, adding or removing interface cards
requires partial disassembly of the computer, reconfiguring the software and
re-
booting the system, thereby increasing system down-time.
In Figure 8, there is shown a peripheral expansion technique, according
to the present invention, wherein input peripheral devices 40 (e.g., bar code
reader, POS keypad, electronic weight scale, magnetic stripe reader, etc.) are
preferably connected to the keyboard port 34 of the IIO controller 6 in a
serial,
daisy chain configuration and output peripheral devices 38 (e.g., pole
display,
video monitor, printer, etc.) are preferably connected to the serial port 36
of the
I/O controller 6. Using this approach, no special I/O interface card nor
special
computer is required. Additionally, only two I/O ports, namely, a keyboard
port
34 and a serial port 36, are used to support many peripheral devices. The
input
peripheral devices can be freely integrated with or removed from the system
simply by coupling or uncoupling their respective cables.
In the keyboard chain of devices, an RS-232 input peripheral device 40
(or other peripheral device which does not output data in keyboard format) may
be incorporated into the point-of-sale system by preferably using an
intelligent
keyboard wedge interface which converts the serial data format of the input
device 40 into standard keyboard data format. Generally, the physical location
of the input peripheral devices is not critical. However, since the
conventional
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101-key computer keyboard has no wedge interface (since its output is already
in standard keyboard data format), it is preferably connected as the last
component in the chain of devices. The wedge interface may be part of the
device cable connection (i.e., external to the input peripheral device 40) or
it may
alternatively be integrated within the input device 40, as illustrated in
Figure 9.
Referring now to Figure 9, the wedge interface circuit is shown
functionally as including a pair of switches 42 and an interface control
circuit 44.
The switches 42 may either be in a pass-through state (default) or may be in a
transmit state. When an input peripheral device 40 has no data available for
transmission, the switches 42 will be in the default pass-through state (as
shown
in Figure 9). As the name suggests, an input device 40 configured with the
switches 42 in the pass-through state basically functions as a conduit through
which data may freely pass, thereby allowing other input peripheral devices to
communicate directly with the I/O controller. When the switches 42 are in the
transmit state, all downstream devices which are connected to the particular
input device 40 (i.e., those input devices that are connected further away
from
the I/O controller in the keyboard daisy chain) are electrically disconnected
from
the data bus and the input device 40 is enabled for communication with the I/O
controller.
If an input peripheral device 40 has data to be transmitted to the I/O
controller, the interface will first monitor the traffic on the data bus to
determine
if another input device is presently communicating with the IIO controller.
Preferably, only one input device 40 may communicate with the I/O controller
at
any given time, thus avoiding bus contention problems which may otherwise
occur. Therefore, when one input device is communicating with the I/O
controller, all other input devices will preferably monitor the bus and
maintain
their pass-through configuration, regardless of whether or not they have data
to
transmit.
When the bus is available for transmission (i.e., a break has been
detected), the interface control circuit 44 of the input peripheral device 40
will
change the state of the switches 42 so as to electrically disconnect the
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downstream input devices from the data_bus, thereby allowing the input device
40 to transmit its data to the I/O controller. While transmitting its data,
the
upstream input devices (i.e., those peripheral devices that are connected
closer
to the I/O controller in the serial keyboard daisy chain) monitor the bus and
maintain their pass-through state. After the input device 40 has completed its
data transmission, the interface control circuit 44 changes the state of the
switches 42 back to the default pass-through state.
If an input peripheral device 40 has data to be transmitted to the I/O
controller and the data bus is busy, the interface control circuit 44 will
preferably
store the data from the input device 40, for example in memory, until a break
is
detected on the bus. Once the bus becomes available, the stored data from the
interface control circuit 44 is subsequently transmitted to the I/O controller
in the
manner described above. If an input device 40 includes multiple interfaces,
each
interface will preferably independently store its data and monitor the data
bus
1 S until the bus is free, and then each interface will transmit its stored
data in turn.
Preferably, the keyboard wedge interface performs a conversion of the
data it receives from the input peripheral device 40, for example RS-232
format,
into standard keyboard data format. Using this approach, all input peripheral
devices will be communicating with the I/O controller in a compatible data
format
(i.e., keyboard data format). This eliminates the need for an 1/O controller
having
multiple interface cards, one for each data format used.
When the interface circuit is not communicating with the I/O controller, it
preferably monitors and records all activities between the keyboard and the
I/O
controller. For example, if the "Caps Lock" key is pressed, the interface
circuit
will make the proper case inversion such that the I/O controller always
receives
the correct characters from the input peripheral device. The interface circuit
also
preferably supports bidirectional dialog with the I/O controller if the
standard
keyboard is not present or is not functioning properly. This allows the I/O
controller to function without generating a "Keyboard Error" interrupt, even
if the
standard keyboard and/or input peripheral devices are not installed.
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The wedge interface circuit may be formed as an external unit, preferably
integrated with the peripheral device cable. This cable would allow standard
(i.e., off-the-shelf) point-of-sale peripheral devices that do not output data
in
standard keyboard format, and do not have an internal wedge interface, to be
used with the POS system of the present invention, thereby keeping overall
system costs down. An exemplary external wedge interface circuit, formed in
accordance with 'the present invention, is illustrated in the electrical
schematic
diagram of Figure 10. As shown in Figure 10, the interface circuit includes a
connector 50, preferably a 25-pin DB25 connector, for operatively coupling the
interface circuit to the output of an input peripheral device. The circuit
further
includes a microprocessor or microcontroller 54, such as an 80C51
microcontroller or equivalent, for performing the required data format
conversion
and bus control functions previously described. Power for the interface
circuit
of Figure 9 may be provided through pin 16 of connector 50 or, alternatively,
external power may be provided through connector jack 64. The wedge
interface circuit preferably includes connectors 60 and 62 to operatively
connect
the interface circuit, and therefore an input peripheral device to which the
interface circuit is connected, between upstream and downstream devices in the
keyboard daisy chain. Connectors 60 and 62 are preferably keyboard-type
connectors, such as 5-pin DIN connectors or equivalent.
Connector 60 preferably receives data from a downstream input
peripheral device which is connected thereto. Connector 62 preferably outputs
data either directly from an adjacent downstream peripheral device, through
connector 60 (e.g., when the interface is in a pass-through state) or from the
peripheral device coupled to connector 50, after the data has been converted
by
the microcontroller 54 (e.g., when the interface is in a transmit state).
Regardless of the state of the interface circuit, the data output from
connector
62 will preferably be in a format compatible with the UO controller port to
which
the chain of peripheral devices is connected. It is to be appreciated that if
the
interface circuit is integrated internally with the input peripheral device,
connector
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50 may be eliminated and the data from the input device would preferably be
directly presented to the microcontroller 54.
Before being presented to the microcontroller 54, it may first be necessary
to invert the data signal from the input peripheral device (attached to
connector
50) by an invertor circuit, preferably realized as a general purpose
transistor 52.
The microcontrolfer 54 can preferably be configured to accept a wide range of
RS-232 protocol parameters and to operate with various attributes, as dictated
by the settings of switches 56, preferably dual in-line pin (DIP) switches,
operatively connected to the microcontroller 54. Such communications
parameters, for example, baud rate, number of data/stop bits and parity option
(on or off), may preferably be set by switches 56.
Preferably, the clock line and data line, which forms the bus
interconnecting the input peripheral devices in the POS system, are
respectively
connected to a pair of commercially available analog multiplexers or switches
58.
Each analog switch 58 has a control input terminal and is ideally the
functional
equivalent of a single-pole single-throw mechanical switch. The signal at the
control input terminal, preferably a binary logic signal (such as zero or five
volts),
controls whether the switch 58 is in an "open" or "closed" state. A switch
control
line 66, connecting the microcontroller 54 to the control input terminals of
the
analog switches 58, preferably allows the microcontroller 54 to simultaneously
open or close the switches 58 under program control.
Ordinarily, the microcontroller 54 preferably generates an appropriate
logic signal on switch control line 66 which maintains the switches 58 in a
closed
state. When the analog switches 58 are closed, the interface circuit is
configured as a pass-through device, thereby allowing a downstream peripheral
device, coupled through connector 60, to communicate with the 1/O controller
(i.e., the clock and data lines of connectors 60 and 62 are respectively
operatively connected together). When the analog switches 58 are opened, the
device coupled to connector 60 becomes electrically disconnected from the bus
and communication between the microcontroller 54 and the I/O controller can
commence through connector 62. Microcontroller 54 preferably monitors the
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clock fine from connector 60 to determine whether the data bus is available
and
accordingly makes the appropriate decision as to what state the analog
switches
58 should be in (i.e., the pass-through state or the transmit state).
It should gibe appreciated that any type of peripheral device can be
connected to the microcontroller 54 by proper selection of the connector 50,
conversion circuit and firmware running on the microcontroller 54. Moreover,
once the peripheral output data is converted to standard keyboard data format,
any number of peripherals can be chained together. When another peripheral
is operating, the remaining peripheral devices simply pass the data along to
the
I/O controller without interference. This is particularly advantageous in
terms of
system expansion capability.
Referring to Figure 12, there is shown a preferred I/O controller node,
formed in accordance with the present invention. The I/O controller node
preferably includes an IIO controller 6 with a CRT display or monitor 38
1 S connected to a serial communications port 35 of the I/O controller 6. The
I/O
controller 6 further includes a keyboard port 34 to which a plurality of point-
of-
sale input peripheral devices are connected in a serial daisy chain
arrangement.
Typical POS peripherals for use with the present invention include a bar code
reader 70, a POS keypad 72, a magnetic stripe reader 74, an electronic weight
scale 76 and a standard computer keyboard 78. As shown in Figure 12, POS
input peripherals which do not ordinarily output their data in standard
keyboard
data format (for example, the bar code reader 70 or electronic weight scale
76)
are preferably connected to the daisy chain bus via intelligent wedge
interface
cables 80 and 82. The interface cables 80 and 82 preferably receive and
convert the non-standard data format to a standard keyboard data output format
(or other compatible data format) for communicating with the IIO controller 6,
as
previously discussed.
In communicating with the plurality of I/O controllers 6, the master
controller 4 will preferably append identification information, for example,
in the
form of a data header or equivalent identification tag, to data received from
the
server 2 (see Figure 2). This identification information preferably specifies
the
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particular peripheral device to ultimately receive the transmitted instruction
or
data. Each I/O controller 6 is connected to the network bus and receives the
data stream from the master controller 4. Subsequently, each I/O controller 6
analyzes the header information associated with the transmitted data. If the
header includes identification information which corresponds to an individual
I/O
controller 6, then that particular I/O controller 6 will pass the data onto
the
peripheral devices connected thereto.
While the master controller 4 and I/O controllers 6 are illustrated as
standalone devices, it should be appreciated that integration of the master
controller 4 within the server 2 or integration of the I/O controller 6 with
one of
the associated system peripherals is contemplated as being within the scope of
the present invention.
A distributed computer network, formed in accordance with the present
invention, is provided which is particularly well-suited for use with a point-
of-sale
system. The distributed computer network of the present invention is an open
system which allows the connection of virtually unlimited peripheral devices
without reducing available input/output ports. Furthermore, the distributed
network allows connection/disconnection of peripheral devices without
disassembling, re-configuring, or re-booting the system, thus reducing system
down-time.
Although illustrative embodiments of the present invention have been
described herein with reference to the accompanying drawings, it is to be
understood that the invention is not limited to those precise embodiments, and
that various other changes and modifications may be effected therein by one
skilled in the art without departing from the scope or spirit of the
invention.
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