WO2000051006A1

WO2000051006A1 - Parallel port cable assembly

Info

Publication number: WO2000051006A1
Application number: PCT/GB2000/000692
Authority: WO
Inventors: Balaji Baktha
Original assignee: SCM Microsystems Ltd; SCM Microsystems Inc
Current assignee: SCM Microsystems Ltd; Identiv Inc
Priority date: 1999-02-26
Filing date: 2000-02-25
Publication date: 2000-08-31
Anticipated expiration: 2001-08-26

Abstract

A cable assembly is formed with a plurality of multi-pin terminals attached to predetermined locations of a multi-strand cable where groups of strands thereof serve to interconnect predefined groups of pins of the plurality of terminals. Various groups of strands of the cable assembly provide a bus-like connection for the first terminal to be connected to a parallel port of a host computer, the second terminal to a peripheral device, and the third terminal to a printer. In the preferred embodiment compliant with the IEEE 1284 parallel interface, the bus-like connection provides access by all three terminals to the data lines of the parallel port, and provides access by the first and second terminals to the control/status lines of the parallel port, and provides access by the second and third terminals to the control/status lines generated by a pass-through port of the peripheral device. In this way, a minimum number of cables and terminals is needed.

Description

PARALLEL PORT CABLE ASSEMBLY

This invention relates generally to connection of peripheral devices to a host computer system, and more particularly to a cable assembly for a parallel interface with a pass-through port.

In the last few years, a considerable market has appeared for externally connectable peripheral devices. Example of such a peripheral device may be a mass storage device such as a hard disk, a computer tape drive, a floppy disk drive, a flash memory card or a CD ROM drive. This type of portable mass storage device is useful for backing up data onto a tape, installing software from a CD ROM onto a computer system not normally having a CD ROM drive or for transferring large amounts of data between computer systems such as between an office and a home computer. Other examples of portable peripheral devices include modems, network interfaces, scanners, and digital handheld devices.

These portable peripheral devices are designed to interface with a standard port of a host system. Often installation simply requires connection of the device to the host computer system and the loading of suitable software drivers onto the host computer system from a supplied floppy disk. Usually the software installation is completely automatic. These external peripheral devices are therefore easier to install than ones that must be installed partly or wholly inside the host system. The latter type requires installation inside the host system or at least the installation of an interface card into the internal bus of the host system. In either cases, the cover of the host system needs be removed for installation and is therefore inconvenient and unsuitable for inexperienced users.

Many of the above described devices connect via a parallel interface to the parallel port of a host computer system. However, a host computer system typically has only one parallel port intended for connection to a printer. When that only parallel port is taken by the parallel interface, there will be none left for connection to a printer or another parallel peripheral device. In view of that, many of the parallel interfaces also incorporate a pass-through port for the printer such that when the external peripheral is idle, the host is able to access the printer via the pass-through port provided at the peripheral device. Thus, the incorporation of a peripheral device with a pass-through port often necessitates additional cabling and repositioning of an existing printer relative to the host computer system and the peripheral device.

These and additional objects are accomplished by improvements in the cabling and terminals arrangement for interconnecting the host computer with the peripheral device and the printer.

According to the present invention there is provided a cable assembly comprising a plurality of multi-pin terminals attached to predetermined locations of a multi-strand cable where groups of strands thereof serve to interconnect predefined groups of pins of the plurality of terminals. The various groups of strands provide various buses for carry signals between the connected devices.

In the preferred embodiment, the cable assembly is formed by two cables each having one end thereof converging into a first terminal, and with the other ends terminating respectively at second and third terminals. The cable assembly provides a bus-like connection for the first terminal to be connected to a parallel port of a host computer, the second terminal to a peripheral device, and the third terminal to a printer.

In the preferred embodiment compliant with the IEEE 1284 parallel interface, the bus-like connection provides access by all three terminals to the data lines of the parallel port, and provides access by the first and second terminals to the control/status lines of the parallel port, and provides access by the second and third terminals to the control/status lines of a pass- through port of the peripheral device.

In this way, a minimum number of cables and terminals is needed, since only one cable assembly with terminals each for connection to a device is required. Whereas, in the prior art, a first cable having a pair of terminals interconnects between the host computer and the peripheral device and a second cable having a pair of terminals interconnects between the printer and the peripheral device.

In the preferred embodiment, the power to the peripheral device is fed through the third terminal. In this way, the need for a separate power cable to the prior art arrangement is avoided. This preferred power connector arrangement allows a neat desktop arrangement as there are no separate power cables and the pass- through cable attached to the peripheral bay.

Additional objects, features, and advantages of the present invention will be understood from the following description of its preferred embodiments, which description should be taken in conjunction with the accompanying drawings.

The invention will now be described by way of example with reference to the drawings in which:

Fig. 1 is a schematic diagram illustrating how a printer is conventionally connected to a parallel port of a computer system;

Fig. 2A is a schematic diagram showing a conventional arrangement in which a peripheral device has an integrated parallel interface which is coupled on one hand to a parallel port of a host computer system and on another hand via a pass-through port to a printer;

Fig. 2B is a schematic diagram showing another conventional arrangement in which the parallel interface shown in Fig. 2A is detached from the peripheral device and relocated close to the parallel port of the host computer system;

Fig. 3 A is a schematic diagram of the cable assembly for a parallel peripheral device with printer pass-through, according to a preferred embodiment of the present invention; Fig. 3B is an illustration of a cable assembly corresponding to the cable configuration shown in Fig. 3A:

Fig. 4 is a detailed schematic illustration of the internal connections of the cable assembly, according to one embodiment of the invention;

Fig. 5 is a detailed schematic illustration of the internal connections of the cable assembly, according to a preferred embodiment of the invention; and

Fig. 6 is a functional block diagram of the parallel interface module of the parallel interface associated with a peripheral device

Fig. 1 is a schematic diagram illustrating how a printer is conventionally connected to a parallel port of a computer system. A host computer system 10 has a parallel port 12 for connection to a preferred external parallel peripheral device such as a printer 20. The printer 20 is connected to the parallel port 12 via a parallel cable 21. The specification of a standard parallel interface typically allows a maximum of three meters of cable between the host system and the parallel peripheral device. Thus the printer 20 is usually positioned adjacent or close to the host computer system 10 as shown in Fig. 1.

As described in the background section, other portable peripheral devices may also be connected externally to the host computer system via its parallel port. This is accomplished by a parallel interface that interfaces between the host computer system and the peripheral device. The parallel interface may be implemented as a separate unit or integrated with the peripheral device itself.

Fig. 2A is a schematic diagram showing a conventional arrangement in which a peripheral device 30 has a parallel interface 40 integrated therewith. The peripheral device has a peripheral port 32 that is coupled to a peripheral interface port 42 of the parallel interface. The parallel interface 40 has two additional ports 44 and 46 for coupling respectively to the host computer system 10 and the printer 20.

An interface parallel cable 16 interconnects between the host computer system's parallel port 12 and the parallel interface's interface parallel port 44. Similarly, a printer parallel cable 26 interconnects between the printer and the parallel interface's interface pass-through port 46. By connecting the printer to the pass-through port 46, the host computer has access to the printer via the parallel port 12 of the host computer system when the peripheral device 30 is not accessed.

As can be seen from Fig. 2A. unlike the configuration shown in Fig. 1, the printer is no longer attached directly to the host computer system, but instead passes through the parallel interface which is located with the peripheral device. However, this arrangement necessitates either repositioning of the printer 20 relative to the host computer system 10 or a longer printer cable 26.

An alternative that avoids having to reposition the printer or to use a longer printer cable is to place the parallel interface 40 close to the parallel port of the host computer system so that the printer cable connects to it at the host computer as is usually the case.

Fig. 2B is a schematic diagram showing an alternative conventional arrangement in which the parallel interface 40 shown in Fig. 2A is detached from the peripheral device and relocated close to the parallel port of the host computer system. Typically, the parallel interface 40 is mounted directly onto a connector for the parallel port 12 of the host computer system. As before, the peripheral interface 40 comprises three ports 42, 44, 46. The interface parallel port 44 is coupled to the parallel port 12 of the host computer system. The interface peripheral port 42 is coupled via a cable 36 to the peripheral device's peripheral port 32. The interface pass-through parallel port 46 is coupled via a printer cable 26' to the printer 20.

As can be seen from Fig. 2B. with the placement of the interface 40 and hence its pass-through port 46 close to the host computer system, the parallel cable 26' required for the printer^'s connection to the pass-through port will be substantially similar to the cable 21 (See Fig. 1) for direct connection to the host computer system. While this arrangement avoids the repositioning of the printer or the lengthening its cable, it does require a separate parallel interface which may not be very convenient. Indeed, in many applications this configuration is impractical because the connection between the peripheral device 30 and the interface 40 must be kept very short.

Fig. 3 A is a schematic diagram of the cable assembly for a parallel peripheral device with printer pass-through, according to a preferred embodiment of the present invention. The peripheral device 30 is coupled to an integrated parallel interface 40 via the interface peripheral port 42. A cable assembly comprises a cable 60 between a terminal 14 and a terminal 54, and a cable 70 between the terminal 14 and a terminal 24. The terminal 14 is a multi-pin terminal for connecting to the parallel port 12 of the host computer system 10. The terminal 54 is a multi-pin terminal for connecting to the interface parallel port 52 of the parallel interface 40. The terminal 24 is a multi-pin terminal for connecting to the parallel printer cable 70a, which in turn is connecting to the parallel printer 20.

As will be described later, the two cables 60 and 70 are both multi-strand and form a bus architecture for the three terminals 14, 54 and 24. Thus, even not explicitly shown in Fig. 3 A, some strands of the cable 60 are actually connected to, or becomes, some strands of the cable 70. As both the cable 60 and cable 70 merge into the terminal 14, another way to view this configuration is that of a single cable with the terminal 14 connected to some group of strands thereof between its two ends.

In the preferred embodiment, provision is made for power to the peripheral device to be supplied by the cable assembly. This is accomplished by one of the three terminals to be adapted to receive power to the cable assembly where one or more strands delivers the power to the peripheral device 30. In the preferred embodiment, the terminal 24 has a sub-terminal 26 embedded in it that allows power to be fed from an external power source (not shown). One or more stands in the cable assembly then carries the power to the parallel interface 40. Fig. 3B is an illustration of a preferred cable assembly corresponding to the schematics shown in Fig. 3 A. The terminal 14 is a DB-25 connector for detachably connecting to a standard parallel port of a personal computer. Two cables 60 and 70 emerge from the terminal 14. On one hand, the cable 60 terminates at the terminal 54. The terminal 54 is a multi-conductor terminal and is typically permanently attached to, or formed directly on, a printed circuit board in the parallel interface 40. On the other hand, the cable 70 terminates at the terminal 24. The terminal 24 is a Centronics connector for detachably connecting to a standard parallel printer 20.

The terminal 24 has the sub-terminal 26 embedded in it and comprises of a power jack connector for inputting power into the cable assembly and ultimately to the parallel interface 40.

The advantage of this cable configuration is that the connection to the parallel interface 40 is simplified from two to one connectors. Finally, the topology of the cable connection between the printer 20 and the host computer system 10 is not changed from that of a standalone printer connection. Thus, no repositioning of an existing printer is required.

Fig. 4 is a detailed schematic illustration of the internal connections of the cable assembly, according to one embodiment of the invention. The host computer system 10 communicates with the peripheral interface 40 via a strand group 61 which is a subset of the strands of the cable 60. In this case, the strand group 61 essentially carries the signals in the parallel lines 11 of the parallel port of the host computer system. As will be described later, a parallel interface module 100 in the peripheral interface either interfaces the signals to a peripheral port 42, or in a pass-through mode, relates the necessary signals to the printer 20 via a strand group 62. The strand group 62 is a subset of strands of the cable 60 and, after it is routed through the terminal 14, becomes a strand group 70. In this way the printer has access to the host computer system's parallel port when the peripheral interface 40 operates in the pass-through mode. Fig. 5 is a detailed schematic illustration of the internal connections of the cable assembly, according to a preferred embodiment of the invention. This embodiment is compliant with the IEEE 1284 parallel interface specification. The IEEE 1284 standard. "Standard Signaling Method for a Bi-directional Parallel Peripheral Interface for Personal Computers", was approved for final release in March of 1994.

One feature of the IEEE 1284 parallel interface standard is to provide a quasi bus architecture for a plurality of parallel devices to be interlinked. In essence, the data signals of the parallel port are carried in a data bus that are accessed by all the parallel devices, whereas the control/status signals of the parallel port are decoded and regenerated as processed control/status signals by a parallel interface for the benefit of the next parallel device downstream of the regenerated signals.

Referring to Fig. 5, for the sake of clarity, the parallel signals contains in the lines 11 of the parallel port in Fig. 4 are shown explicitly as separate data lines 13 and control/status lines 15. At the terminal 14, the signals in the data lines 13 are carried by a data bus formed, on one hand, by a strand group 63 connecting to the terminal 54 and, on the other hand, by a strand group 73 connecting to the terminal 24. In this way, all three terminals 14, 54 and 24, and hence the host computer system 10, the peripheral device 30 and the printer 10 have common access to the data bus.

Also at the terminal 14, the signals in the control/status lines 15 are carried by a strand group 65 connecting to the terminal 54. In this way, the parallel interface 40 of the peripheral device 30 has access to the control/status signals of the parallel port of the host computer system.

At the parallel interface 40, the control/status signals are decoded and regenerated as processed control/status signals by the parallel interface module 100 and returned from the terminal 54 via a strand group 67 and then a strand group 77 to the printer 20 through the terminal 24. In the preferred embodiment, the strand groups 63, 65 and 67 are part of the cable 60. Similarly, the strand groups 73 and 77 are part of the cable 70. In particular, the strand group 67 runs continuously from the terminal 54 as part of the cable 60 and becomes the strand group 77 after it reaches the terminal 14, and from there runs to the terminal 24 as part of the cable 70.

Fig. 6 is a functional block diagram of the parallel interface module 100. The parallel interface module 100 is preferably implemented as an application specific integrated circuit chip (ASIC) that comprises a command decoder 110, a register array 120, an IEEE 1284 protocol controller 130, a uni/bi-dir nibble controller 140, and a peripheral interface controller 150.

The command decoder 110 decodes the type of operation from the signals in the strand group 65 from the host interface. After a successful selection, the host computer system 10 (Fig. 3 A) can initiate a transfer cycle by first writing the appropriate command in the registers of the register array 120. All operations are controlled through these registers. The value written is then decoded and the appropriate mode of operation is enabled.

The IEEE 1284 Protocol Controller interprets the IEEE 1284 events and selects/deselects other portions of the parallel interface module 100. After power-up, the parallel interface module is in the unassigned mode. All control lines from the host via the strand group 65 are connected to the pass-through port via the strand group 67. Similarly, all status lines from the pass-through port via the strand group 67 are connected to the host via the protocol controller and strand group 65.

The IEEE 1284 standard supports several transfer modes, such as the uni-directional standard parallel port (SPP) mode, or the bi-directional EPP and the ECP modes. In the uni-directional mode, the data is transferred through strand group 65. In the bidirectional mode, the status and control lines are redefined for the mode in use. The uni/bi-dir nibble controller 140 transfers data to the host into two nibbles (four bits each) that are read through the status lines in the strand group 65. The uni-dir portion of the controller 140 splits the eight bit data to the host into five plus three bits. The five bits are read through the status lines and the remaining three bits are read through the control lines in the strand group 65. The peripheral interface controller 150 controls the data flow and generates all control signals to the peripheral device 30 via the interface peripheral port 42.

The detailed pin connections of the terminals 14, 54. and 24 will not be described as they are well defined by the standard IEEE 1284 specification.

It will be appreciated from the above, therefore, that by having a single cable assembly comprising of a terminal each for the peripheral device, the host computer and a printer, the invention provide a particularly simple and effective solution to the problems stated in the introduction.

While the embodiments of the various aspects of the present invention that have been described are the preferred implementation, those skilled in the art will understand that variations thereof may also be possible. Therefore, the invention is entitled to protection within the full scope of the appended claims.

Claims

1. A cable assembly for interconnecting a host computer system, and at least a peripheral device and a printer for passing signals therebetween, comprising: a first multi-pin terminal for connection to a parallel port of said host computer system; a second multi-pin terminal for connection to a parallel interface of said peripheral device; a third multi-pin terminal for connection to said printer; a first multi-strand cable between said first and second terminals; and a second multi-strand cable between said first and third terminals, a first group of strands of said first cable interconnecting between a first group of pins of said first and said second terminals; a second group of strands of said first cable having first and second ends, with its first ends connecting to a second group of pins of said second terminal; and a third group of strands of said second cable having third and fourth ends, with its fourth ends connecting to a first group of pins of said third terminal; and the second ends of the second group of strands of said first cable being joined onto the third ends of the third group of strands of said second cable at said first terminal.

2. A cable assembly as in 1 , wherein: said parallel port of said host computer system comprises data signals and host control and status signals; said parallel interface of said first peripheral device comprises interface control and status signals; said first cable interconnects between a first portion said first and second terminals to provide said data signals and said host control and status signals thereto; and said second cable interconnects between a second portion of said first and third terminals to provide said data signals thereto, and interconnects between a third portion of said second and third terminals to provide said interface status signals thereto.

3. A cable assembly as in 1-2, wherein said parallel interface of said peripheral device further comprises means for selectively passing signals between said first terminal and said third terminal.

4. A cable assembly as in 1-2, wherein the parallel port of the host computer system and the parallel interface of said peripheral device complies with the IEEE 1248 specification.

5. A cable assembly as in 1-2, wherein said peripheral device includes a network adapter.

6. A cable assembly as in 1 -2, wherein said peripheral device includes a mass storage.

7. A cable assembly as in 1 -2, wherein said peripheral device includes a flash memory card reader.

8. A cable assembly as in 1-2, wherein said peripheral device includes an image scanner.

9. A cable assembly as in 1-2, wherein said first peripheral device includes a portable digital device.

10. A cable assembly as in 1-2, wherein said second terminal is permanently connected to said parallel interface of said peripheral device.

11. A cable assembly as in 1-2, wherein said first terminal is detachably connected to said parallel port of said host computer system.

12. A cable assembly as in 1-2, wherein said third terminal is detachably connected to said parallel interface of said second peripheral device.

13. A cable assembly as in 1-2. wherein said third terminal includes a power cable for supplying power to said peripheral device.

14. A cable assembly, comprising: a multi-strand cable; a plurality of multi-pin terminals attached to predetermined locations along said multi-stand cable for interconnecting a parallel port of a host computer system, one or more peripheral devices and a parallel printer; and said multi-stand cable having a plurality of groups of strands partitioned therefrom, each group of strands for interconnecting predefined groups of pins of two or more of said plurality of multi-pin terminals.

15. A cable assembly as in 14, wherein: the one or more peripheral devices include one with a parallel interface; said parallel port of said host computer system comprises data signals and host control and status signals; said parallel interface of said peripheral device has a terminal for interface control and status signals; a first group of strands interconnects between said first and second terminals to provide said data signals and said host control and status signals thereto; and a second group of strands interconnects between said first and third terminals to provide said data signals thereto, and interconnects between said second and third terminals to provide said interface control and status signals thereto.

16. A peripheral device, comprising: a parallel interface having a parallel port and a parallel pass-through port; a multi-strand cable having one end thereof connected to said parallel interface; a plurality of multi-pin terminals attached to predetermined locations along said multi-stand cable for interconnecting a host computer system, one or more peripheral devices and a parallel printer; and said multi-stand cable having a plurality of groups of strands partitioned therefrom, each group of strands for interconnecting predefined groups of pins of two or more of said plurality of multi-pin terminals.