Apparatus for allowing multiple parallel port devices to share a single parallel port

Claim 1

An apparatus for coupling a printer parallel port device and a plurality of non-printer parallel port devices to a single parallel port of a personal computer so that each of said parallel port devices can be accessed and controlled by software running in the personal computer with switching between said plurality of parallel port devices being performed under software control and without user intervention, said apparatus comprising: command decoder means, coupled to said parallel port, for decoding signals from said parallel port into one of (i) commands for selecting a predetermined one of said parallel port devices or (ii) data or (iii) control for passing to a previously selected one of said parallel port devices, said command decoder means includes a dedicated line, when asserted, selects the printer parallel port device as said predetermined one of said parallel port devices; b) a plurality of gate means, each of said plurality of gate means is coupled to said command decoder means, for passing signals between said parallel port and said predetermined one of said parallel port devices when said command decoder means has selected said predetermined one of said parallel port devices and for maintaining said predetermined one of said parallel port devices in an idle state when said command decoder means has deselected said predetermined one of said parallel port devices.

Claim 2

An apparatus for coupling a printer parallel port device and a plurality of non-printer parallel port devices to a single parallel port of a personal computer so that each of said parallel port devices can be accessed and controlled by software running in the personal computer with switching between said plurality of parallel port devices being performed under software control and without user intervention, said apparatus comprising: command decoder means, coupled to said parallel port, for decoding signals from said parallel port into one of (i) commands for selecting a predetermined one of said parallel port devices or (ii) data or (iii) control for passing to a previously selected one of said parallel port devices, said command decoder means includes a dedicated line, when asserted, selects the printer parallel port device as said predetermined one of said parallel port devices; b) a plurality of gate means, each of said plurality of gate means is coupled to said command decoder means, for passing signals between said parallel port and said predetermined one of said parallel port devices when said command decoder means has selected said predetermined one of said parallel port devices and for maintaining said predetermined one of said parallel port devices in an idle state when said command decoder means has deselected said predetermined one of said parallel port devices.

Claim 7

An apparatus for coupling a printer parallel port device and a plurality of non-printer parallel port devices to a single parallel port of a personal computer so that each of said parallel port devices can be accessed and controlled by software running in said personal computer with switching between said plurality of parallel port devices being performed under software control and without user intervention, said apparatus comprising: a) command decoder means for coupling said parallel port for decoding signals from said parallel port into one of commands for selecting a predetermined one of said parallel port devices or data or control for passing to a previously selected one of said parallel port devices, said command decoder means including i) a sequence detector means for determining, when enabled, whether signals received from said parallel port are for identifying one of said non-printer parallel port devices, said sequence detector means including at least one detector, coupled to said parallel port and a decoder means, adapted to be initialized with a set of values, each value representing a predetermined one of said parallel port devices, and a comparator, coupled to said at least one detector and said parallel port, adapted to compare data signals from said parallel port device with said values and to assert a trigger signal upon determining that a match exists, and ii) said decoder means for generating a control signal upon receipt of said trigger signal selecting one of said plurality of non-printer parallel port devices and deselecting the other ones of said plurality of non-parallel port devices and for generating an enable signal for enabling said sequence detector means; and b) a plurality of gate means, each coupled to said command decoder means for coupling to a predetermined one of said parallel port devices for passing signals between said parallel port and its associated parallel port device when said command decoder means has selected its said associated parallel port device and maintaining its said associated parallel port device in an idle state when said command decoder means has deselected its said associated parallel port device.

Claim 8

An apparatus for coupling a printer parallel port device and a plurality of non-printer parallel port devices to a single parallel port of a personal computer so that each of said parallel port devices can be accessed and controlled by software running in said personal computer with switching between said plurality of parallel port devices being performed under software control and without user intervention, said apparatus comprising: a) command decoder means for coupling said parallel port for decoding signals from said parallel port into one of commands for selecting a predetermined one of said parallel port devices or data or control for passing to a previously selected one of said parallel port devices, said command decoder means including i) a sequence detector means for determining, when enabled, whether signals received from said parallel port are for identifying one of said non-printer parallel port devices, said sequence detector means including at least one detector, coupled to said parallel port and a decoder means, adapted to be initialized with a set of values, each value representing a predetermined one of said parallel port devices, and a comparator, coupled to said at least one detector and said parallel port, adapted to compare data signals from said parallel port device with said values and to assert a trigger signal upon determining that a match exists, and ii) said decoder means for generating a control signal upon receipt of said trigger signal selecting one of said plurality of non-printer parallel port devices and deselecting the other ones of said plurality of non-parallel port devices and for generating an enable signal for enabling said sequence detector means; and b) a plurality of gate means, each coupled to said command decoder means for coupling to a predetermined one of said parallel port devices for passing signals between said parallel port and its associated parallel port device when said command decoder means has selected its said associated parallel port device and maintaining its said associated parallel port device in an idle state when said command decoder means has deselected its said associated parallel port device.

Claim 11

An apparatus for coupling a printer parallel port device and a plurality of non-printer parallel port devices to a single parallel port of a personal computer so that each of said parallel port devices can be accessed and controlled by software running in said personal computer with switching between said plurality of parallel port devices being performed under software control and without user intervention, said apparatus comprising: a) command decoder means for coupling said parallel port for decoding signals from said parallel port into one of commands for selecting a predetermined one of said parallel port devices or data or control for passing to a previously selected one of said parallel port devices said command decoder means including i) sequence detector means for determining, when enabled, whether signals received from said parallel port are for identifying one of said non-printer parallel port devices and, if so, generating a trigger signal, and ii) decoder means for generating a control signal upon receipt of said trigger signal selecting one of said plurality of non-printer parallel port devices and deselecting the other ones of said plurality of non-parallel port devices and for generating an enable signal for enabling said sequence detector means, said decoder means includes a master slave flip-flop for coupling to said parallel port and coupled to said sequence detector means and a plurality of gate means and sequence select logic, said master slave flip-flop being adapted to generate a signal for activating one of said plurality of gate means and deactivating other of said plurality of gate means; and b) said plurality of gate means, each coupled to said command decoder means, for coupling to a predetermined one of said parallel port devices, for passing signals between said parallel port and its associated parallel port device when said command decoder means has selected its said associated parallel port device and maintaining its said associated parallel port device in an idle state when said command decoder means has deselected its said associated parallel port device.

Claim 12

An apparatus for coupling a printer parallel port device and a plurality of non-printer parallel port devices to a single parallel port of a personal computer so that each of said parallel port devices can be accessed and controlled by software running in said personal computer with switching between said plurality of parallel port devices being performed under software control and without user intervention, said apparatus comprising: a) command decoder means for coupling said parallel port for decoding signals from said parallel port into one of commands for selecting a predetermined one of said parallel port devices or data or control for passing to a previously selected one of said parallel port devices said command decoder means including i) sequence detector means for determining, when enabled, whether signals received from said parallel port are for identifying one of said non-printer parallel port devices and, if so, generating a trigger signal, and ii) decoder means for generating a control signal upon receipt of said trigger signal selecting one of said plurality of non-printer parallel port devices and deselecting the other ones of said plurality of non-parallel port devices and for generating an enable signal for enabling said sequence detector means, said decoder means includes a master slave flip-flop for coupling to said parallel port and coupled to said sequence detector means and a plurality of gate means and sequence select logic, said master slave flip-flop being adapted to generate a signal for activating one of said plurality of gate means and deactivating other of said plurality of gate means; and b) said plurality of gate means, each coupled to said command decoder means, for coupling to a predetermined one of said parallel port devices, for passing signals between said parallel port and its associated parallel port device when said command decoder means has selected its said associated parallel port device and maintaining its said associated parallel port device in an idle state when said command decoder means has deselected its said associated parallel port device.

Claim 13

An apparatus for coupling a printer parallel port device and a plurality of non-printer parallel port devices to a single parallel port of a personal computer so that each of said parallel port devices can be accessed and controlled by software running in said personal computer with switching between said plurality of parallel port devices being performed under software control and without user intervention, said apparatus comprising: a) command decoder means for coupling said parallel port for decoding signals from said parallel port into one of commands for selecting a predetermined one of said parallel port devices or data or control for passing to a previously selected one of said parallel port devices; and b) a plurality of gate means, each coupled to said command decoder for coupling to a predetermined one of said parallel port devices for passing signals between said parallel port and its associated parallel port device when said command decoder means has selected its said associated parallel port device and maintaining its said associated parallel port device in an idle state when said command decoder has deselected its said associated parallel port device, wherein each of said plurality of said gate means comprises a tri-state buffer and a transparent latch for coupling to a printer controller of said printer and said parallel port, said tri-state buffer is adapted to send signals from said printer controller to said parallel port and said transparent latch is adapted to send signals from said parallel port to said printer controller.

Claim 14

An apparatus for coupling a printer parallel port device and a plurality of non-printer parallel port devices to a single parallel port of a personal computer so that each of said parallel port devices can be accessed and controlled by software running in said personal computer with switching between said plurality of parallel port devices being performed under software control and without user intervention, said apparatus comprising: a) command decoder means for coupling said parallel port for decoding signals from said parallel port into one of commands for selecting a predetermined one of said parallel port devices or data or control for passing to a previously selected one of said parallel port devices; and b) a plurality of gate means, each coupled to said command decoder for coupling to a predetermined one of said parallel port devices for passing signals between said parallel port and its associated parallel port device when said command decoder means has selected its said associated parallel port device and maintaining its said associated parallel port device in an idle state when said command decoder has deselected its said associated parallel port device, wherein each of said plurality of said gate means comprises a tri-state buffer and a transparent latch for coupling to a printer controller of said printer and said parallel port, said tri-state buffer is adapted to send signals from said printer controller to said parallel port and said transparent latch is adapted to send signals from said parallel port to said printer controller.

Claim 15

A system having a hardware component and a software component, said hardware component for coupling a printer parallel port device and a plurality of non-printer parallel port devices to a single parallel port of a personal computer so that each of said parallel port devices can be accessed and controlled by said software component running in said personal computer with switching between said plurality of parallel port devices being performed under software control and without user intervention, wherein said hardware component comprises: a) command decoder means for coupling to said parallel port for decoding signals from said parallel port into one of commands for selecting a predetermined one of said parallel port devices or data and control for passing to a previously selected one of said parallel port devices; b) plurality of gate means, each coupled to said command decoder and for coupling to a predetermined one of said parallel port devices for passing signals between said parallel port and its associated parallel port device when said command decoder means has selected its said associated parallel port device and maintaining its said associated parallel port device in an idle state when said command decoder has deselected its said associated parallel port device; and said software component comprises: a program running in said personal computer which operates to cause a switch from a first parallel port device to a second parallel port device Y wherein when a request is to be made of said second device, the software: i) interrupts a task for controlling the first device; ii) sends an illegal instruction or command over the parallel port to the then connected first parallel port device; iii) sends a command to select said second parallel port device to said command decoder means through the parallel port; and iv) activates the task which controls the second parallel port device.

Claim 16

A system having a hardware component and a software component, said hardware component for coupling a printer parallel port device and a plurality of non-printer parallel port devices to a single parallel port of a personal computer so that each of said parallel port devices can be accessed and controlled by said software component running in said personal computer with switching between said plurality of parallel port devices being performed under software control and without user intervention, wherein said hardware component comprises: a) command decoder means for coupling to said parallel port for decoding signals from said parallel port into one of commands for selecting a predetermined one of said parallel port devices or data and control for passing to a previously selected one of said parallel port devices; b) plurality of gate means, each coupled to said command decoder and for coupling to a predetermined one of said parallel port devices for passing signals between said parallel port and its associated parallel port device when said command decoder means has selected its said associated parallel port device and maintaining its said associated parallel port device in an idle state when said command decoder has deselected its said associated parallel port device; and said software component comprises: a program running in said personal computer which operates to cause a switch from a first parallel port device to a second parallel port device Y wherein when a request is to be made of said second device, the software: i) interrupts a task for controlling the first device; ii) sends an illegal instruction or command over the parallel port to the then connected first parallel port device; iii) sends a command to select said second parallel port device to said command decoder means through the parallel port; and iv) activates the task which controls the second parallel port device.