Abstract:
A method and system for operating an input/output circuit for driving peripheral devices controlled by an embedded system. For increasing the overall system availability the invention proposes to add some limited, repeatedly-performed status storing functionality preferably into a register storage of the I/O devices. The stored information can be easily exploited (i.e., read out from external of the input/output devices) via the controller of the embedded system.

Description:
FIELD OF THE INVENTION 
     The present invention relates to improvements of system availability of networked computer systems. In particular, it relates to method and system for operating an input/output circuit for driving peripheral devices within an embedded system. 
     BACKGROUND OF THE INVENTION 
     The present invention is generally applicable in computer networks comprising a plurality of computers. Particular additional advantages can be taken of it when said plurality of computers has some inner structure of ‘competence distribution’ exist, in particular a structure in which a first type of server computers and a second type of more or less dedicated control computer, in particular embedded controllers, exist which have only a reduced technical equipment, as e.g., no hard disk, or display unit, or keyboard, etc. 
     Although the present invention has a very broad scope implied by its inherent technical abstractness it will be discussed in here with reference to a larger enterprise computer network which is schematically depicted in FIG.  1 . 
     Such a multi-server/multi-user networked environment comprises a huge number of peripheral devices  36 , e.g. terminals, printers, storage devices, sensors, actuators and the like, which are connected with and controlled by a server cluster  10  having a plurality of CPUs  11 , a memory controller  22  cooperating with a cache device  14  and a plurality of memory cards  12  via a respective system bus or a adapted switching device. 
     To supervise the communication between said server cluster  10  (left) and said peripheral devices  36  (right), so called embedded systems  18  are used to sense and control the so-called Input/Output devices  26  e.g., so-called I/O cards. These embedded systems are hosted on the so-called power/controller cards  18  and are dedicated computing units, for example a so-called Power PC which is used without the usual man/machine interface. 
     For the purpose of version consistency required for operating the peripheral devices  36  without major problems as well as for cost reasons neither said I/O cards  26  nor embedded controllers  18  do possess an own persistent software storage, like a hard disk, in which multiple versions of a software could be stored and executed. 
     Instead, and with additional reference to FIG. 2, a more detailed, schematic representation of a prior art I/O card is given. There is provided a controller interface  9  connecting to an ASIC chip  28  in which the control logic is implemented for controlling the operation of the individual drive devices  42 ,  32  for driving the peripheral devices. In an example depicted in FIG. 2, this is an electrical-to-optical and vice versa, Signal Converter  42  cooperating with a plurality of optical device drivers  32 . Thus, said system comprises a controller means  22  and an input/output circuit ( 26 ) with an ASIC  28  and sensor response means  32  for driving said device  42 . 
     Further, a clock  41  is provided for supplying said converter and the ASIC with a respective clock signal. 
     Via the functional interface  14  the operational signals are transferred which are required to use the peripheral devices. 
     Via said controller interface the ASIC  28 , the so-called FGA, receives data signals and a clock signal. This implementation allows to even communicate with the FGA (ASIC)  28  when the clock on the card is defective or powerless due to a short somewhere on the card. In this case the sense and control lines of the FGA can still be used to identify the root cause of the problem. 
     In order to focus now on the disadvantages of prior art, the system availability in computer system environments like those described above is addressed now in more detail: 
     Although, a variety of efforts is made to absolutely minimize the duration where a computer system environment or a subsystem is not able to perform its task due to a software or a hardware failure, e.g., redundant controllers, redundant peripheral devices, driver code runs in only one, unique version, etc., the system availability is not sufficiently provided yet in prior art. 
     From other computer system environments that have real-time requirements, and wherein consequently the system availability is extremely important, various techniques like keeping persistent states, trace points, etc., are known to improve system availability. 
     This, however, is not applicable to the embedded systems due to the specific hardware configuration of said embedded systems, and the intended absence of e.g., a hard disk and a respective tracing logic in the I/O card itself. 
     It would be desirable to apply such techniques like keeping persistent states, trace points, etc. to other computer system environments or subsystems as well, for example to profit from them in the above mentioned embedded systems in order to increase their system availability. 
     It is thus an object of the present invention to improve the system availability in an environment comprising embedded systems. 
     SUMMARY OF THE INVENTION 
     The foregoing and other objects are achieved by the present invention comprising a method and system for operating an input/output circuit for driving peripheral devices controlled by an embedded system. For increasing the overall system availability the invention proposes to add some limited repeatedly performed status storing functionality preferably into a register storage of the I/O devices. The information can be easily exploited, (i.e., read out from external of the input/output devices) via the controller of the embedded system. 
     Said additional logic “add-on”, which is for example implemented in an ASIC in the embedded system, repeatedly generates status information reflecting the status of an associated input/output device, continuously stores said status information in an input/output storing means, for example, in a register included in said ASIC, and keeps said status information available to be requested by a controller communicating with the ASIC logic in the input/output circuit. 
     Said regular storing of status information then enables the controller, for example in case of a controller reboot or when a redundantly provided controller takes over the job of a first controller which had a breakdown before, to initiate a helpful response to be issued by a sensor response means. For example the response will be from an Optical-to-Electrical signal converter, in a case when an optical peripheral device is to be operated or when a fibre-optic signal transmission is performed by said converter. 
     The helpfulness for the purposes of improved system availability is that said response reflects the current drive status of said exemplary converter device. 
     Thus when the controller software reads the (current) status information from said input/output storage means of said input/output circuit, it is enabled to comparing said response with the stored status information. Thus the controller is enabled to continue the operation of said sensor response means dependent of the compare result. 
     When for example, the freshly sensed status is the same as that one read out from the register, then the rebooted controller or the stand-by redundant controller can continue operation without restarting/rebooting/reinitializing the sensor response circuit which in the worst case would terminate a running communication between server and peripheral devises. 
     By the foregoing implementation, time is saved and the system availability is increased. The solution profits from the fact that it is possible for the operating system, and thus for the controller, to read and write the I/O address space. Thus an I/O register or the like can be used as a normal RAM for storing said important status information. 
     Advantageously, a register is used for storing the status information, because a power drop then has the same effect on the register content as on the current sense information at the sensor response device, (i.e., such that there is no defined status which can be relied on) and thus the logical conclusion that a restart of the device is required is easy and error-free to reach. 
     Advantageously, a cold-start indicator flag is additionally provided which is comprised of said status information. This flag can be evaluated by the controller in the above situation prior to any other information. When the flag is ‘on’, then the controller must initialize the dependent device. In this single case a reboot of the device is required. 
     The present invention is thus advantageously applicable when increased system availability—nearly permanent—of the components is required. This is in particular the case in the above-mentioned type of systems when the controllers are configured redundantly. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention is illustrated by way of example and is not limited by the shape of the figures of the accompanying drawings in which: 
     FIG. 1 is a schematic block diagram showing the most essential elements used in the environment of a clustered server area communicating with a prior art an I/O circuit system, survived by an embedded control system, for operating peripheral devices, 
     FIG. 2 is a schematic block diagram showing the most essential elements of a prior art I/O circuit used in FIG. 1 showing some more details, 
     FIG. 3 is a schematic block diagram according to FIG. 2 but disclosing the inventional use of a storage according to a preferred aspect of the inventional method, and 
     FIG. 4 is a schematical block diagram showing the basic steps and the control flow of an embodiment of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With general reference to the figures and with special reference now to FIG. 3 an inventive input/output device  26  is described in more detail. The input/output device  26  comprises a plurality of optical driver devices  32 , a clock device  41 , an electrical-to-optical multiplexing device  42  which represents the above mentioned sensor response means, a hardware chip device  28  that controls said input/output device  26 , and an inventive input/output storage means  40  for storing the above-mentioned status information. The storage means is an input/output register accessible by the operating system of the server, see back to FIG.  1 . 
     In the register storage  40 , the ASIC  28  logic repeatedly stores status information of the converter  42 . Thus, this information can be used later on when it is requested by a controller via the controller interface which is discussed next below with reference to FIG.  4 . 
     FIG. 4 is a schematic block diagram showing the basic steps and the control flow of an embodiment of the inventive method. On a failure of the controller means  18 , said controller is rebooted at step  410 . After the controller  18  has resumed operation, it reads a cold start flag from the register  40  located with the ASIC  28  inside the input/output device circuit  26  at step  420 . 
     If the cold start flag is set to YES, see the YES branch of decision at  430 , the system is recognized to be in stand-by status, as depicted at step  440 , and waits for activation, i.e., a restart initiated by the controller, at step  445 . 
     If the cold start flag is set to NO, see the NO-branch of decision  430 , the status information reflecting the current status of said input/output device  26  is sensed at step  450  into the controller  18 . 
     Then the status information which was already (repeatedly) been stored in the input/output register storage  40  located on the input/output device  26  is read at step  460  and compared, at step  470 , to the status information freshly sensed by the controller means  18 . This leads to a decision at step  480  of whether the read and the sensed information is identical or not. 
     If identical results are present, see the YES-Branch of decision  480 , and the regular operation of the system is continued, at step  490 , meaning that the system continues its operation at the point where the disruption occurred. 
     Otherwise, along the NO-branch wherein the result of the comparison (at  480 ) does not yield identical results, then a failure is reported and the input/output device ( 26 ) is re-initialized, at step  500 , and an optional service can be triggered provide for repairing the breakdown system elements. 
     Thus, as revealed from the foregoing description, the present invention represents a large step forward to increase the overall system availability in those systems having the specific properties detailed herein. 
     In the foregoing specification the invention has been described with reference to a specific exemplary embodiment thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention as set forth in the appended claims. The specification and drawings are accordingly to be regarded as illustrative rather than in a restrictive sense. 
     The present invention can be realized in hardware, software, or a combination of hardware and software. A tool according to the present invention can be realized in a centralized fashion in one computer system, or in a distributed fashion where different elements are spread across several interconnected computer systems. Any kind of computer system or other apparatus adapted for carrying out the methods described herein is suited. A typical combination of hardware and software could be a general purpose computer system with a computer program that, when being loaded and executed, controls the computer system such that it carries out the client or server specific steps of the methods described herein. 
     The present invention can also be embedded in a computer program product, which comprises all the features enabling the implementation the respective steps of the methods described herein, and which—when loaded in one or more computer systems—is able to carry out these methods. 
     Computer program means or computer program in the present context mean any expression, in any language, code or notation, of a set of instructions intended to cause a system having an information processing capability to perform a particular function either directly or after either or both of the following: a) conversion to another language, code or notation; b) reproduction in a different material form.