(12) United States Patent
`Tasler
`
`111111
`
`1111111111111111111111111111111111111111111111111111111111111
`US006895449B2
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 6,895,449 B2
`May 17,2005
`
`(54) FLEXIBLE INTERFACE FOR
`COMMUNICATION BETWEEN A HOST AND
`AN ANALOG I/O DEVICE CONNECTED TO
`THE INTERFACE REGARDLESS THE TYPE
`OF THE I/O DEVICE
`
`(75)
`
`Inventor: Michael Tasler, Wuerzburg (DE)
`
`(73) Assignee: Labortechnik Tasler GmbH,
`Wuerzburg (DE)
`
`( *) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.c. 154(b) by 369 days.
`
`(21) Appl. No.: 10/219,105
`
`(22) Filed:
`
`Aug. 15, 2002
`
`(65)
`
`Prior Publication Data
`
`US 2002/0199037 A1 Dec. 26, 2002
`
`Related U.S. Application Data
`
`(62) Division of application No. 09/331,002, filed on Jun. 14,
`1999.
`
`(30)
`
`Foreign Application Priority Data
`
`Mar. 4, 1997
`Mar. 3, 1998
`
`(DE) ......................................... 197 08 755
`(EP) ................................. PCT/EP98/01187
`
`Int. CI? ................................................ G06F 13/14
`(51)
`(52) U.S. CI. ............................... 710/16; 710/8; 710/64;
`709/220
`(58) Field of Search ................................ 710/8, 16, 64,
`710/11, 12, 15, 62, 63; 703/23, 24, 25;
`709/220, 222
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`5,548,783 A * 8/1996 Jones et al. ................... 710/16
`5,596,628 A * 1/1997 Klein ...................... 379/93.11
`5,628,030 A * 5/1997 Tuckner ...................... 710/64
`6,012,113 A * 1/2000 Tuckner ...................... 710/64
`6,266,711 B1 * 7/2001 Ishikawa et al. ............... 710/8
`6,363,081 B1 * 3/2002 Gase .......................... 370/466
`6,725,293 B1 * 4/2004 Nakayama et al.
`........... 710/36
`6,728,844 B2 * 4/2004 Sanada et al.
`.............. 711/152
`* cited by examiner
`Primary Examiner-Jeffrey Gaffin
`Assistant Examiner-Harold Kim
`(74) Attorney, Agent, or Firm-Glenn Patent Group;
`Michael A. Glenn
`(57)
`
`ABSTRACT
`
`An interface device (10) provides fast data communication
`between a host device with input/output interfaces and a data
`transmit/receive device, wherein the interface device (10)
`comprises a processor means (13), a memory means (14), a
`first connecting device (12) for interfacing the host device
`with the interface device, and a second connecting device
`(15) for interfacing the interface device (10) with the data
`transmit/receive device. The interface device (10) is config(cid:173)
`ured by the processor means (13) and the memory means
`(14) in such a way that, when receiving an inquiry from the
`host device via the first connecting device (12) as to the type
`of a device attached to the host device, regardless of the type
`of the data transmit/receive device, the interface device
`sends a signal to the host device via the first connecting
`device (12) which signals to the host device that it is
`communicating with an input/output device.
`
`18 Claims, 2 Drawing Sheets
`
`1284
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`Papst Licensing GmbH & Co., KG.
`Petitioner - Apple, Inc.
`Patent Owner - Papst Licensing GmbH & Co., KG.
`IPR2017-00156
`EXH. 2002
`
`1
`
`

`

`u.s. Patent
`
`May 17, 2005
`
`Sheet 1 of 2
`
`US 6,895,449 B2
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`13
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`

`US 6,895,449 B2
`
`1
`FLEXIBLE INTERFACE FOR
`COMMUNICATION BETWEEN A HOST AND
`AN ANALOG I/O DEVICE CONNECTED TO
`THE INTERFACE REGARDLESS THE TYPE
`OF THE I/O DEVICE
`
`RELATED APPLICATIONS
`
`This application is a divisional application of copending
`application Ser. No. 09/331,002 filed Jun. 14, 1999.
`
`DESCRIPTION
`
`The present invention relates to the transfer of data and in
`particular to interface devices for communication between a
`computer or host device and a data transmit/receive device
`from which data is to be acquired or with which two-way
`communication is to take place.
`Existing data acquisition systems for computers are very
`limited in their areas of application. Generally such systems
`can be classified into two groups.
`In the first group host devices or computer systems are
`attached by means of an interface to a device whose data is
`to be acquired. The interfaces of this group are normally
`standard interfaces which, with specific driver software, can
`be used with a variety of host systems. An advantage of such
`interfaces is that they are largely independent of the host
`device. However, a disadvantage is that they generally
`require very sophisticated drivers which are prone to mal(cid:173)
`function and which limit data transfer rates between the
`device connected to the interface and the host device and
`vice versa. Further, it is often very difficult to implement
`such interfaces for portable systems and they offer few
`possibilities for adaptation with the result that such systems
`offer little flexibility.
`The devices from which data is to be acquired cover the
`entire electrical engineering spectrum. In a typical case, it is
`assumed that a customer who operates, for example, a
`diagnostic radiology system in a medical engineering envi(cid:173)
`ronment reports a fault. A field service technician of the
`system manufacturer visits the customer and reads system
`log files generated by the diagnostic radiology system by
`means a portable computer or laptop for example. If the fault
`cannot be localized or if the fault is intermittent, it will be
`necessary for the service technician to read not only an error
`log file but also data from current operation. It is apparent
`that in this case fast data transfer and rapid data analysis are
`necessary.
`Another case requiring the use of an interface could be,
`for example, when an electronic measuring device, e.g. a
`multimeter, is attached to a computer system to transfer the
`data measured by the multimeter to the computer. Particu(cid:173)
`larly when long -term measurements or large volumes of data
`are involved is it necessary for the interface to support a high
`data transfer rate.
`From these randomly chosen examples it can be seen that
`an interface may be put to totally different uses. It is
`therefore desirable that an interface be sufficiently flexible to
`permit attachment of very different electrical or electronic
`systems to a host device by means of the interface. To
`prevent operator error, it is also desirable that a service
`technician is not required to operate different interfaces in
`different ways for different applications but that, if possible,
`a universal method of operating the interface be provided for
`a large number of applications.
`To increase the data transfer rates across an interface, the
`route chosen in the second group of data acquisition systems
`
`5
`
`15
`
`2
`for the interface devices was to specifically match the
`interface very closely to individual host systems or computer
`systems. The advantage of this solution is that high data
`transfer rates are possible. However, a disadvantage is that
`the drivers for the interfaces of the second group are very
`closely matched to a single host system with the result that
`they generally cannot be used with other host systems or
`their use is very ineffective. Further, such types of interface
`have the disadvantage that they must be installed inside the
`10 computer casing to achieve maximum data transfer rates as
`they access the internal host bus system. They are therefore
`generally not suitable for portable host systems in the form
`of laptops whose minimum possible size leaves little internal
`space to plug in an interface card.
`A solution to this problem is offered by the interface
`devices of IOtech (business address: 25971 Cannon Road,
`Cleveland, Ohio 44146, USA) which are suitable for laptops
`such as the WaveBook/512 (registered trademark). The
`interface devices are connected by means of a plug-in card,
`20 approximately the size of a credit card, to the PCMCIA
`interface which is now a standard feature in laptops. The
`plug-in card converts the PCMCIA interface into an inter(cid:173)
`face known in the art as IEEE 1284. The said plug-in card
`provides a special printer interface which is enhanced as
`25 regards the data transfer rate and delivers a data transfer rate
`of approximately 2 MBps as compared with a rate of approx.
`1 MBps for known printer interfaces. The known interface
`device generally consists of a driver component, a digital
`signal processor, a buffer and a hardware module which
`30 terminates in a connector to which the device whose data is
`to be acquired is attached. The driver component is attached
`directly to the enhanced printer interface thus permitting the
`known interface device to establish a connection between a
`computer and the device whose data is to be acquired.
`In order to work with the said interface, an interface-
`specific driver must be installed on the host device so that
`the host device can communicate with the digital signal
`processor of the interface card. As described above, the
`driver must be installed on the host device. If the driver is
`40 a driver developed specifically for the host device, a high
`data transfer rate is achieved but the driver cannot be easily
`installed on a different host system. However, if the driver is
`a general driver which is as flexible as possible and which
`can be used on many host devices, compromises must be
`45 accepted with regard to the data transfer rate.
`Particularly in an application for multi -tasking systems in
`which several different tasks such as data acquisition, data
`display and editing are to be performed quasi(cid:173)
`simultaneously, each task is normally assigned a certain
`50 priority by the host system. A driver supporting a special
`task requests the central processing system of the host
`device for processor resources in order to perform its task.
`Depending on the particular priority assignment method and
`on the driver implementation, a particular share of processor
`55 resources is assigned to a special task in particular time slots.
`Conflicts arise if one or more drivers are implemented in
`such a way that they have the highest priority by default, i.e.
`they are incompatible, as happens in practice in many
`applications. It may occur that both drivers are set to highest
`60 priority which, in the worst case, can result in a system
`crash.
`EP 0685799 A1 discloses an interface by means of which
`several peripheral devices can be attached to a bus. An
`interface is connected between the bus of a host device and
`65 various peripheral devices. The interface comprises a finite
`state machine and several branches each of which is
`assigned to a peripheral device. Each branch comprises a
`
`35
`
`4
`
`

`

`US 6,895,449 B2
`
`3
`data manager, cycle control, user logic and a buffer. This
`known interface device provides optimal matching between
`a host device and a specific peripheral device.
`The specialist publication IBM Technical Disclosure
`Bulletin, Vol. 38, No. OS, page 245; "Communication
`Method between Devices through FDD Interface" discloses
`an interface which connects a host device to a peripheral
`device via a floppy disk drive interface. The interface
`consists in particular of an address generator, an MFM
`encoder/decoder, a serial/parallel adapter and a format signal
`generator. The interface makes it possible to attach not only
`a floppy disk drive but also a further peripheral device to the
`FDD host controller of a host device. The host device
`assumes that a floppy disk drive is always attached to its
`floppy disk drive controller and communication is initiated
`if the address is correct. However, this document contains no
`information as to how communication should be possible if
`the interface is connected to a multi-purpose interface
`instead of to a floppy disk drive controller.
`It is the object of the present invention to provide an 20
`interface device for communication between a host device
`and a data transmit/receive device whose use is host device(cid:173)
`independent and which delivers a high data transfer rate.
`This object is achieved by an interface device according
`to claim 1 or 12 and by a method according to claim 15.
`The present invention is based on the finding that both a
`high data transfer rate and host device-independent use can
`be achieved if a driver for an input/output device customary
`in a host device, normally present in most commercially
`available host devices, is utilized. Drivers for input/output
`devices customary in a host device which are found in
`practically all host devices are, for example, drivers for hard
`disks, for graphics devices or for printer devices. As how(cid:173)
`ever the hard disk interfaces in common host devices which
`can be, for example, IBM PCs, IBM-compatible PCs, Com(cid:173)
`modore PCs, Apple computers or even workstations, are the
`interfaces with the highest data transfer rate, the hard disk
`driver is utilized in the preferred embodiment of the inter(cid:173)
`face device of the present invention. Drivers for other 40
`storage devices such as floppy disk drives, CD-ROM drives
`or tape drives could also be utilized in order to implement
`the interface device according to the present invention.
`As described in the following, the interface device accord(cid:173)
`ing to the present invention is to be attached to a host device 45
`by means of a multi-purpose interface of the host device
`which can be implemented, for example, as an SCSI inter(cid:173)
`face or as an enhanced printer interface. Multi-purpose
`interfaces comprise both an interface card and specific driver
`software for the interface card. The driver software can be 50
`designed so that it can replace the BIOS driver routines.
`Communication between the host device and the devices
`attached to the multi -purpose interface then essentially takes
`place by means of the specific driver software for the
`multi-purpose interface and no longer primarily by means of 55
`BIOS routines of the host device. Recently however drivers
`for multi -purpose interfaces can also already be integrated in
`the BIOS system of the host device as, alongside classical
`input/output interfaces, multi-purpose interfaces are becom(cid:173)
`ing increasingly common in host devices. It is of course also 60
`possible to use BIOS routines in parallel with the specific
`driver software for the multi-purpose interface, if this is
`desired.
`The interface device according to the present invention
`comprises a processor means, a memory means, a first
`connecting device for interfacing the host device with the
`interface device, and a second connecting device for inter-
`
`4
`facing the interface device with the data transmit/receive
`device. The interface device is configured by the processor
`means and the memory means in such a way that the
`interface device, when receiving an inquiry from the host
`5 device via the first connecting device as to the type of a
`device attached to the host device, sends a signal, regardless
`of the type of the data transmit/receive device, to the host
`device via the first connecting device which signals to the
`host device that it is communicating with an input/output
`10 device. The interface device according to the present inven(cid:173)
`tion therefore simulates, both in terms of hardware and
`software, the way in which a conventional input/output
`device functions, preferably that of a hard disk drive. As
`support for hard disks is implemented as standard in all
`15 commercially available host systems, the simulation of a
`hard disk, for example, can provide host device-independent
`use. The interface device according to the present invention
`therefore no longer communicates with the host device or
`computer by means of a specially designed driver but by
`means of a program which is present in the BIOS system
`(Basic Input/Output System) and is normally precisely
`matched to the specific computer system on which it is
`installed, or by means of a specific program for the multi(cid:173)
`purpose interface. Consequently, the interface device
`25 according to the present invention combines the advantages
`of both groups. On the one hand, communication between
`the computer and the interface takes place by means of a
`host device-specific BIOS program or by means of a driver
`program which is matched to the multi-purpose interface
`30 and which could be regarded as a "device-specific driver".
`On the other hand, the BIOS program or a corresponding
`multi-purpose interface program which operates one of the
`common input/output interfaces in host systems is therefore
`present in all host systems so that the interface device
`35 according to the present invention is host device(cid:173)
`independent.
`In the following, preferred embodiments of the present
`invention will be explained in more detail with reference to
`the drawings enclosed, in which:
`FIG. 1 shows a general block diagram of the interface
`device according to the present invention; and
`FIG. 2 shows a detailed block diagram of an interface
`device according to a preferred embodiment of the present
`invention.
`FIG. 1 shows a general block diagram of an interface
`device 10 according to the present invention. A first con(cid:173)
`necting device 12 of the interface device 10 can be attached
`to a host device (not shown) via a host line 11. The first
`connecting device is attached both to a digital signal pro(cid:173)
`cessor 13 and to a memory means 14. The digital signal
`processor 13 and the memory means 14 are also attached to
`a second connecting device 15 by means of bi-directional
`communication lines (shown for all lines by means of two
`directional arrows). The second connecting device can be
`attached by means of an output line 16 to a data transmit/
`receive device which is to receive data from the host device
`or from which data is to be read, i.e. acquired, and trans(cid:173)
`ferred to the host device. The data transmit/receive device
`itself can also communicate actively with the host device via
`the first and second connecting device, as described in more
`detail in the following.
`Communication between the host system or host device
`and the interface device is based on known standard access
`65 commands as supported by all known operating systems
`(e.g. DOS, Windows, Unix). Preferably, the interface device
`according to the present invention simulates a hard disk with
`
`5
`
`

`

`US 6,895,449 B2
`
`5
`
`5
`a root directory whose entries are "virtual" files which can
`be created for the most varied functions. When the host
`device system with which the interface device according to
`the present invention is connected is booted and a data
`transmit/receive device is also attached to the interface
`device 10, usual BIOS routines or multi-purpose interface
`programs issue an instruction, known by those skilled in the
`art as the INQUIRY instruction, to the input/output inter(cid:173)
`faces in the host device. The digital signal processor 13
`receives this inquiry instruction via the first connecting 10
`device and generates a signal which is sent to the host device
`(not shown) again via the first connecting device 12 and the
`host line 11. This signal indicates to the host device that, for
`example, a hard disk drive is attached at the interface to
`which the INQUIRY instruction was sent. Optionally, the 15
`host device can send an instruction, known by those skilled
`in the art as "Test Unit Ready", to the interface device to
`request more precise details regarding the queried device.
`Regardless of which data transmit/receive device at the
`output line 16 is attached to the second connecting device, 20
`the digital signal processor 13 informs the host device that
`it is communicating with a hard disk drive. If the host device
`receives the response that a drive is present, it then sends a
`request to the interface device 10 to read the boot sequence
`which, on actual hard disks, normally resides on the first 25
`sectors of the disk. The digital signal processor 13, whose
`operating system in stored in the memory means 14,
`responds to this instruction by sending to the host device a
`virtual boot sequence which, in the case of actual drives,
`includes the drive type, the starting position and the length 30
`of the file allocation table (FAT), the number of sectors, etc.,
`known to those skilled in the art. Once the host device has
`received this data, it assumes that the interface device 10
`according to a preferred embodiment of the present inven(cid:173)
`tion is a hard disk drive. In reply to an instruction from the
`host device to display the directory of the "virtual" hard disk
`drive simulated by the interface device 10 with respect to the
`host device, the digital signal processor can respond to the
`host device in exactly the same way as a conventional hard
`disk would, namely by reading on request the file allocation
`table or FAT on a sector specified in the boot sequence,
`normally the first writable sector, and transferring it to the
`host device, and subsequently by transferring the directory
`structure of the virtual hard disk. Further, it is possible that
`the FAT is not read until immediately prior to reading or
`storing the data of the "virtual" hard disk and not already at
`initialization.
`In a preferred embodiment of the present invention, the
`digital signal processor 13, which need not necessarily be
`implemented as a digital signal processor but may be any 50
`other kind of microprocessor, comprises a first and a second
`command interpreter. The first command interpreter carries
`out the steps described above whilst the second command
`interpreter carries out the read/write assignment to specific
`functions. If the user now wishes to read data from the data 55
`transmit/receive device via the line 16, the host device sends
`a command, for example "read file xy", to the interface
`device. As described above, the interface device appears to
`the host device as a hard disk. The second command
`interpreter of the digital signal processor now interprets the
`read command of the host processor as a data transfer
`command, by decoding whether "xy" denotes, for example,
`a "real-time input" file, a "configuration" file or an execut(cid:173)
`able file, whereby the same begins to transfer data from the
`data transmit/receive device via the second connecting
`device to the first connecting device and via the line 11 to the
`host device.
`
`6
`Preferably, the volume of data to be acquired by a data
`transmit/receive device is specified in a configuration file
`described in the following by the user specifying in the said
`configuration file that a measurement is to last, for example,
`five minutes. To the host device the "real-time input" file
`then appears as a file whose length corresponds to the
`anticipated volume of data in those five minutes. Those
`skilled in the art know that communication between a
`processor and a hard disk consists of the processor trans(cid:173)
`ferring to the hard disk the numbers of the blocks or clusters
`or sectors whose contents it wishes to read. By reference to
`the FAT the processor knows which information is contained
`in which block. In this case, communication between the
`host device and the interface device according to the present
`invention therefore consists of the very fast transfer of block
`numbers and preferably of block number ranges because a
`virtual "real-time input" file will not be fragmented. If the
`host device now wants to read the "real-time input" file, it
`transfers a range of block numbers to the interface device,
`whereupon data commences to be received via the second
`connecting device and data commences to be sent to the host
`device via the first connecting device.
`In addition to the digital signal processor instruction
`memory, which comprises the operating system of the digital
`signal processor and can be implemented as an EPROM or
`EEPROM, the memory means 14 can have an additional
`buffer for purposes of synchronizing data transfer from the
`data transmit/receive device to the interface device 10 and
`data transfer from the interface device 10 to the host device.
`Preferably, the buffer is implemented as a fast random
`access memory or RAM buffer.
`Further, from the host device the user can also create a
`configuration file, whose entries automatically set and con(cid:173)
`trol various functions of the interface device 10, on the
`35 interface device 10 which appears to the host device as a
`hard disk. These settings can be, for example, gain, multi(cid:173)
`plex or sampling rate settings. By creating and editing a
`configuration file, normally a text file which is simple to
`understand with little prior knowledge, users of the interface
`40 device 10 are able to perform essentially identical operator
`actions for almost any data transmit/receive devices which
`can be attached to the second connecting device via the line
`16, thus eliminating a source of error arising from users
`having to know many different command codes for different
`45 applications. In the case of the interface device 10 according
`to the present invention it is necessary for users to note the
`conventions of the configuration file once only in order to be
`able to use the interface device 10 as an interface between
`a host device and almost any data transmit/receive device.
`As a result of the option of storing any files in agreed
`formats in the memory means 14 of the interface device 10,
`taking into account the maximum capacity of the memory
`means, any enhancements or even completely new functions
`of the interface device 10 can be quickly implemented. Even
`files executable by the host device, such as batch files or
`executable files (BAT or EXE files), and also help files can
`be implemented in the interface device, thus achieving
`independence of the interface device 10 from any additional
`software (with the exception of the BIOS routines) of the
`60 host device. On the one hand, this avoids licensing and/or
`registration problems and, on the other hand, installation of
`certain routines which can be frequently used, for example
`an FFT routine to examine acquired time-domain data in the
`frequency domain, is rendered unnecessary as the EXE files
`65 are already installed on the interface device 10 and appear in
`the virtual root directory, by means of which the host device
`can access all programs stored on the interface device 10.
`
`6
`
`

`

`US 6,895,449 B2
`
`7
`In a preferred embodiment of the present invention in
`which the interface device 10 simulates a hard disk to the
`host device, the interface device is automatically detected
`and readied for operation when the host system is powered
`up or booted. This corresponds to the plug-and-play standard 5
`which is currently finding increasingly widespread use. The
`user is no longer responsible for installing the interface
`device 10 on the host device by means of specific drivers
`which must also be loaded; instead the interface device 10
`is automatically readied for operation when the host system 10
`is booted.
`For persons skilled in the art it is however obvious that the
`interface device 10 is not necessarily signed on when the
`computer system is powered up but that a special BIOS
`routine or a driver for a multi-purpose interface can also be 15
`started on the host device during current operation of the
`computer system in order to sign on or mount the interface
`device 10 as an additional hard disk. This embodiment is
`suitable for larger workstation systems which are essentially
`never powered down as they perform, e.g. mail functions or
`monitor processes which run continuously, for example, in
`multi-tasking environments.
`In the interface device according to the present invention
`an enormous advantage is to be gained, as apparent in the
`embodiment described in the following, in separating the
`actual hardware required to attach the interface device 10 to
`the data transmit/receive device from the communication
`unit, which is implemented by the digital signal processor
`13, the memory means 14 and the first connecting device 12,
`as this allows a plurality of dissimilar device types to be 30
`operated in parallel in identical manner. Accordingly, many
`interface devices 10 can be connected to a host device which
`then sees many different "virtual" hard disks. In addition,
`any modification of the specific hardware symbolized by the
`second connecting device 15 can be implemented essentially 35
`without changing the operation of the interface device
`according to the present invention. Further, an experienced
`user can intervene at any time on any level of the existing
`second connecting device by making use of the above
`mentioned option of creating a configuration file or adding 40
`or storing new program sections for the second connecting
`device.
`An important advantage of the interface device 10 of the
`present invention is that it also permits extremely high data
`transfer rates by using, for data interchange, the host device- 45
`own BIOS routines which are optimized for each host device
`by the host device manufacturer or BIOS system
`manufacturer, or by using driver programs which are nor(cid:173)
`mally optimized and included by the manufacturers of
`multi-purpose interfaces. Furthermore, due to the simulation 50
`of a virtual mass storage device, the data is managed and
`made available in such a way that it can be transferred
`directly to other storage media, e.g. to an actual hard disk of
`the host device without, as it were, intervention of the host
`device processor. The only limitation to long-term data 55
`transfer at high speed is therefore imposed exclusively by
`the speed and the size of the mass storage device of the host
`device. This is the case as the digital signal processor 13
`already formats the data read by the data transmit/receive
`device via the second connecting device 15 into block sizes 60
`suitable for a hard disk of the host device, whereby the data
`transfer speed is limited only by the mechanical latency of
`the hard disk system of the host device. At this point, it
`should be noted that normally data flow from a host device
`must be formatted in blocks to permit writing to a hard disk 65
`and subsequent reading from a hard disk, as known by those
`skilled in the art.
`
`8
`The said data transfer rate can be increased further by
`setting up a direct memory access (DMA) or RAM drive in
`the host system. As those skilled in the art know, the setting
`up of a RAM drive requires processor resources of the host
`device, with the result that the advantage of writing the data
`to a hard disk drive of the host device essentially without the
`need for processor resources is lost.
`As described above, a data buffer can be implemented in
`the memory means 14 to permit independence in terms of
`time of the data transmit/receive device attached to the
`second connecting device from the host device attached to
`the first connecting device. This guarantees error-free opera(cid:173)
`tion of the interface device 10 even for time-critical appli-
`cations in multi-tasking host systems.
`FIG. 2 shows a detailed block diagram of an interface
`device 10 according to the present invention.
`A digital signal processor (DSP) 1300 is, in a manner of
`speaking, the heart of the interface device 10. The DSP can
`20 be any DSP but