Abstract:
Methods and a system for operating a programmable device are disclosed. In one embodiment, a method includes accessing a master summary data and loading an original configuration data to configuration registers of the programmable device. The method further includes generating a current summary data by performing a summary operation of a current configuration data of the configuration registers of the programmable device, comparing the current summary data with the master summary data, and performing an exception action if the current summary data does not match with the master summary data.

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 11/904,643, filed Sep. 28, 2007, which claims the priority of U.S. Provisional Patent Application No. 60/906,605, filed Mar. 12, 2007, both of which are incorporated herein by reference. 
    
    
     FIELD OF TECHNOLOGY 
     Embodiments of the present invention relate to the field of electronics. More particularly, embodiments of the present invention relate to configuration data of a programmable device. 
     BACKGROUND 
     A programmable device (e.g., a programmable microcontroller) contains configuration registers which hold configuration data to establish functional blocks (e.g., which perform user-defined logic functions), I/O blocks (e.g., which configures input/output blocks interfacing to external devices), and/or signal routing resources (e.g., which connect the functional blocks to each other and/or the I/O blocks). 
     The configuration data may be represented as configuration bits of configuration registers (e.g., stored as volatile memory). Upon the boot-up of the programmable device, the configuration data stored in non-volatile memory may be copied to the configuration registers of the volatile memory. However, the configuration data residing in the configuration registers may be compromised due to several factors. 
     For example, an unintended software execution may create a write-over condition where improper data may be written to the configuration registers. Additionally, cosmic rays, X-rays, and/or other environmental factors may cause the configuration data to degrade (e.g., flip); these are known as soft errors. These errors (e.g., the write-over, soft errors, etc.) of the configuration data may compromise the functional block, the I/O blocks, and/or the routing resources, thereby rendering the programmable device inoperable for its intended purposes. 
     In case when the programmable device is used in a critical condition (e.g., involving an emergency situation) or life critical function, the reliability of the programmable device becomes ever more critical. For instance, the functionality of an airbag deployment system may rely on the operation of a programmable device. Furthermore, the configuration data (e.g., bits) become more susceptible to the soft errors as the feature size (e.g., a silicon geometry) of the programmable device gets smaller. 
     SUMMARY 
     Accordingly, what is needed is a method and system that can increase the reliability of programmable devices. Embodiments of the present invention provide these advantageous functionalities. 
     One embodiment of the present invention pertains to a method for continuously checking the integrity of configuration data of a programmable device. More specifically, the method includes (a) accessing a master summary data and (b) generating a current summary data by performing a summary operation of current configuration data of configuration registers. The method further includes (c) comparing the current summary data with the master summary data and (d) performing an exception action if the current summary data does not match with the master summary data. Steps (b) through (d) are repeated as long as there is no mismatch between the current summary data and the master summary data. 
     Embodiments also include correcting any data inconsistencies upon detecting a CRC mismatch. Embodiments also include storing one or more CRCs to protect against soft errors of the master CRC. 
     As illustrated in the detailed description, other embodiments also pertain to methods and systems that provide a novel way to check the integrity of the configuration data in programmable devices, and in particular, continuously checking the integrity of the configuration data loaded to the programmable devices in an unobtrusive way. Through utilizing the error checking methods and systems, the embodiments provide more robust and dependable programmable device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Example embodiments are illustrated by way of example and not limitation in the figures of the accompanying drawings, in which like references indicate similar elements and in which: 
         FIG. 1  is a block diagram of an exemplary programmable device with a configuration system utilizing a DMA controller, according to one embodiment. 
         FIG. 2  is a system diagram of the configuration system of  FIG. 1 , according to one embodiment. 
         FIG. 3  is a process flow chart of an exemplary process for loading configuration data to configuration registers based on transaction descriptors, according to one embodiment. 
         FIG. 4  is a process flow chart of an exemplary process for checking the validity of transaction descriptors, according to one embodiment. 
         FIG. 5  is a process flow chart of an exemplary process for loading configuration data to configuration resisters using the DMA controllers, according to one embodiment. 
         FIG. 6  is a block diagram of a programmable device with a system to maintain the integrity of configuration data, according to one embodiment. 
         FIG. 7  is a process flow chart of an exemplary process for iteratively comparing a current cyclic redundant check (CRC) data with a master CRC data to preserve the integrity of configuration data, according to one embodiment. 
     
    
    
     Other features of the present embodiments will be apparent from the accompanying drawings and from the detailed description that follows. 
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the preferred embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the claims. Furthermore, in the detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be obvious to one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the present invention. 
     I. Configuration of Programmable Device Using a DMA Controller 
       FIG. 1  is a block diagram of an exemplary programmable device  100  with a configuration system utilizing a DMA controller  104 , according to one embodiment.  FIG. 1  illustrates a reset  102 , a DMA controller  104 , a cache  106 , a cache control  108 , a processor  110  (e.g., a central processing unit (CPU)), a random access memory (RAM)  112 , a first memory  114 , a local memory  116 , configuration registers  118 , and/or an wait signal  120 , according to one embodiment. 
     The programmable device  100  may be a microcontroller or any programmable device with a DMA controller (e.g., a PLD, a FPGA, etc.). The programmable device  100  may be a programmable system on chip (PSoC), a configurable system on chip (a CSoC), or a field programmable array gate with an embedded microprocessor. The reset  102  may be an input or may be generated internally and delete some or all volatile information stored in the programmable device  100 . The programmable device  100  may be configured when the processor  110  of the programmable device  100  is placed to a non-executing state. For example, once the reset  102  is released, the programmable device  100  may be configured with configuration data (e.g., default configuration data). The reset  102  may include a reset during a run time operation, a master reset during an initialization, a power-on reset, a watchdog reset, and an external reset of the programmable device  100 . 
     The DMA controller  104  is a dedicated data transfer device which reads data from a first memory location to a second memory location. A direct memory access (DMA) based on the DMA controller  104  is efficient because a dedicated piece of hardware (e.g., the DMA controller  104 ) responds to and/or performs a transaction request more quickly than the processor  110 , which may take several read/write cycles to copy an item of data from memory (eg 114) to configuration registers. 
     The cache  106  (e.g., controlled by the cache controller  108 ) is a temporary storage area where frequently accessed data may be stored for rapid access (e.g., by the processor  110 ). The processor  110  may be placed in a reset mode during the configuration process utilizing the DMA controller  104 . The RAM  112  may be a volatile memory dedicated to the processor  110  and/or may also be accessible by the DMAC. The first memory  114  (e.g., non-volatile memory) is used to store program codes (e.g., software, etc.) and/or configuration data. The first memory  114  may be a read only memory (ROM), an EPROM, a flash memory, and/or a non-volatile random access memory (NVRAM). 
     The local memory  116  stores transaction descriptors used to define the behavior of the DMAC which may include configuring the configuration registers  118 . The transaction descriptors may be meta-data which describe the properties (e.g., address, length, type, priority, etc. of data being transferred) of corresponding transactions (e.g., data transfer operations). The local memory  116  may be a volatile memory (e.g., a random access memory). 
     The configuration registers  118  contain registers used for configuring logic blocks of the programmable device, such as configuring input/output resources, programmable analog blocks, programmable digital blocks, routing resources, etc. The number of configuration registers may be quite large on complex programmable devices. The wait signal  120  may be de-asserted to release the processor  110  from the reset mode when the configuration process is completed. 
     In one example embodiment illustrated in  FIG. 1 , a user or an external event may initiate the reset  102  or any other configuration signal of the programmable device  100 . As the reset  102  is released, the DMA controller  104  may load Transaction Descriptors (TSs) to control data transactions described in details in  FIG. 2 . The DMA controller  104  may secure a bus access for data transactions based on a DMA request. 
     With the bus secured, data of the program memory  114  may be transferred to the local memory  116  and/or to the configuration registers  118 . The data transactions utilizing the DMA controller  104  may be faster compared to ones using the processor  110  because the DMA controller  104  may be dedicated to solely moving data between memories and/or registers. 
     Additionally, the data transaction may be transparent to the user of the programmable device  100  because the data transaction is run in the background rather than in the foreground. The processor  110  would take longer if it were to complete the data transaction instead of the DMA controller  104 . 
     Once the data transaction to configure the configuration registers  118  is completed, the wait signal  120  may be de-asserted to the processor  110  to notify the completion of the configuration, thus releasing the processor  110  from the reset mode. When the wait signal  120  is processed by the processor  110 , the processor  110  may commence normal operations (e.g., thus transitioning from the reset state to the runtime mode). 
       FIG. 2  is a system diagram of the configuration system of  FIG. 1 , according to one embodiment.  FIG. 2  illustrates a second memory  200 , a default transaction descriptor (TD)  202 , transaction descriptors  204 , a configuration TD 1  206 A, a configuration TD 2  206 B, a configuration TD 3  206 C, a configuration TD N  206 N, and configuration data  208  along with the DMA controller  104 , the first memory  114 , the local memory  116 , and the configuration registers  118 . 
     The second memory is a non-volatile memory storing the default TD  202 . The default TD  202  is hard coded in the device as opposed to other codes configurable by the user. As the reset  102  of  FIG. 1  is released, the default TD  202  is automatically loaded to the DMA controller  104  to initiate the configuration process. The configuration TDs  204  are transaction descriptors which oversee the configuration process. The configuration TDs  204  may includes one or more fields which include a source address, a destination address, a priority, and a size of data being transferred as well as a transaction type. The configuration TDs  204  may be moved to the local memory  116  when the default TD  202  is processed by the DMA controller  104  (e.g., to perform a transaction to move the configuration TDs  204  to the local memory  116 ). 
     The function of the default TD  202  is to control the movement of config TDs  206  from  114  to  116 . The function of the sequence of TDs in the local memory  116  is to load the configuration registers  118  with the configuration data  208 . 
     The configuration TD 1  206 A, the configuration TD 2  206 B, the configuration TD 3  206 C, and other configuration TDs (e.g., the configuration TD N  206 N) may be chained such that the configuration TD 2  206 B may be automatically processed by the DMA controller  104  after the configuration TD 1  206 A is processed and the configuration TD 3  206 C after the configuration TD 2  206 B. This process may continue until the configuration TD N  206 N is processed. At this time, all the configuration data  208  of the currently selected configuration of the device has been loaded into the configuration registers  118 . The configuration data  208  may be a stream of bits used to configure the functional blocks, I/O blocks, and/or signal routing resources of the programmable device  100  of  FIG. 1 . 
     In one example embodiment, a system to configure the programmable device  100  may include the DMA controller  104  and the local memory  116 . When the reset  102  is released (e.g., to initiate a configuration process), the default TD  202  (e.g., which may be stored in a non-volatile memory) is first loaded to the DMA controller  104  to initiate a transaction to transfer the configuration TDs  204  to the local memory  116 . The validity of the configuration TDs  204  may be checked before the transaction takes place, as will be illustrated in details in  FIG. 4 . 
     At the same time, a DMA request may be processed by the DMA controller  104  to secure bus bandwidth necessary to transfer data (e.g., the configuration TDs  204  and the configuration data  208 ). This DMA request may be triggered automatically on release of reset. Once the bus access is secured, the configuration TDs  204  are loaded to the local memory  116 . The configuration TDs in the local memory  116  may be chained to each other (e.g., sequentially such that when the data transfer defined by one TD completes the data transfer defined by the next TD in the sequence begins automatically). 
     For instance, the configuration TD 1  206 A may be chained to the default TD  202 , the configuration TD 2  206 B to the configuration TD 1  206 A, the configuration TD 3  206 C to the configuration TD 2  206 B, and so forth. As each configuration TD in the TD memory  116  (e.g., the configuration TD 1  206 A, the configuration TD 2  206 B, the configuration TD 3  206 C, the configuration N  206 N) is processed, a memory block defined by it may be transferred from the first memory  114  to the configuration registers  118 . As the TDs in the local memory  116  are processed by the DMA controller  104 , the configuration data  208  are loaded to the configuration registers  118 . 
     The chain of configuration TDs may enable a seamless performance of the configuration process such that only needed portions of the first memory  114  may be copied to the configuration registers  118  rather than copying an entire block of the first memory  114 . The transfer of individual blocks of configuration data defined by each of the configuration TDs may be more efficient because there is less waste of the first memory  114 . 
     For instance, if an entire block of memory required for the configuration of the configuration registers  118  was to be transferred, several large sized blocks of the first memory  114  would be needed to store a different combinations of the configuration data  208 . With the ability to select individual blocks of the first memory  114  from a chunk of the first memory  114  according to the transaction TDs  204 , the transfer of the configuration data  208  would become more efficient. 
     As the configuration TD N  206 N is processed (e.g., writing the last bit of the configuration data  208  to the configuration registers  118 ), the wait signal  120  of  FIG. 1  may be released to communicate to the processor  110  (e.g., reporting the end of the configuration process). Once the processor  110  processes the wait signal  120 , the processor  110  may commence the runtime operation releasing itself from the reset mode. 
       FIG. 3  is a process flow chart of an exemplary process for loading configuration data to configuration registers based on transaction descriptors, according to one embodiment. In operation  302 , a processor (e.g., a CPU) of a programmable device (e.g., PSoC) is placed into a reset state (e.g., during the runtime operation or the initialization of the programmable device). In operation  304 , a default transaction descriptor (e.g., which may be stored in a dedicated non-volatile memory) identifying one or more transaction descriptors (e.g., stored in a non-volatile memory) is issued to a direct memory access (DMA) controller. During the operation, the one or more transaction descriptors may be copied from a non-volatile memory to a volatile memory using the DMA controller. 
     In operation  306 , a set of configuration data are copied from a first memory (e.g., the non-volatile memory) to configuration registers based on the one or more transaction descriptors (e.g., chained) being processed by the DMA controller. Additionally, the processor may be released from the reset state after the last one of the one or more transaction descriptors (e.g., which writes last block of the configuration data to the configuration registers) is executed by the DMA controller. 
       FIG. 4  is a process flow chart of an exemplary process for checking the validity of transaction descriptors, according to one embodiment. The validity of transaction descriptors may be checked to prevent the device from “going crazy” if the first memory  114  is erased and/or corrupted since processing the erased memory as TDs could result in strange and/or unpredictable behavior. In operation  402 , a processor of a programmable device is placed into a reset state. In operation  404 , a default transaction descriptor identifying one or more transaction descriptors is issued to a direct memory access (DMA) controller. In operation  406 , the one or more transaction descriptors are verified prior to copying a set of configuration data from a first memory to configuration registers. When the transaction descriptors are found to be invalid, an event (e.g., halting the loading of the set of configuration data to the configuration registers) may be generated. 
     In one example embodiment, field types of the one or more transaction descriptors may be compared with expected field types of the one or more transaction descriptors (e.g., a source address, a destination address, a priority, and/or a size of the configuration data) to verify the transaction descriptors. When the verification fails, the copying the set of configuration data may be bypassed. In another example embodiment, a checksum or a cyclic redundancy check (CRC) of the one or more transaction descriptors may be performed for the verification. 
       FIG. 5  is a process flow chart of an exemplary process for loading configuration data to configuration resisters through channels enabled by a DMA controller, according to one embodiment. In operation  502 , a direct memory access (DMA) request is generated to a DMA controller in response to a reset of a programmable device (e.g., a PSoC, a FPGA, etc.). During the reset of the programmable device, a processor of the programmable device may be placed in a reset state. In operation  504 , configuration data of the programmable device are automatically loaded to configuration registers of the programmable device using the DMA controller. In operation  506 , a processor of the programmable device is released from the reset state when the configuration data of the programmable device is completely loaded to the configuration registers. 
     II. Continuous Integrity Checking of Configuration Data of Programmable Device 
       FIG. 6  is a block diagram of a programmable device  600  (e.g., a microcontroller, a PLD, a FPGA, etc.) with a system to maintain the integrity of the configuration data, according to one embodiment.  FIG. 6  illustrates a summary data generator  604 , a first memory  606 A, an auxiliary memory  606 B, a master summary data  608 A, a master summary data  608 B, a second memory  610 , a current summary data  612 , and a comparator  614  along with the DMA controller  104 , the processor  110 , the first memory  114 , and the configuration registers  118  of  FIG. 1 . 
     The summary generator  604  generates the current summary data  612  by performing a summary operation of current configuration data of configuration registers of the programmable device  600 . The first memory  606 A and the auxiliary memory  606 B may be a flash memory or any non-volatile memory. The master summary data  608 A may be a summary data obtain through performing a summary operation of the configuration data upon their initial loading to the configuration registers  118 . The master summary data  608 B is optional and may be a duplicate of the master summary data  608 A. 
     The second memory  610  may be a flash memory or any non-volatile memory. The current summary data  612  may be the most recent summary data stored to the second memory  610  until next summary data writes over the current summary data  612  (e.g., thus the next summary data becoming the current summary data  612 ). The comparator  614  may be a device which compares the current summary data  612  with the master summary data  608 A. The comparator may be also used to compare the master summary data  608 A and the master summary data  608 B. 
     The configuration data may be default configuration data or user-defined configuration data. When the configuration data are loaded to the configuration registers  118 , the DMA controller  104  may be used to access (e.g., read) the configuration data to perform a summary operation. The summary operation may be based on one of many methods of checking the integrity of the configuration data, such as redundancy check (e.g., a checksum, a cyclic redundancy check, a horizontal redundancy check, a vertical redundancy check and a cryptographic message digest). 
     Once the master summary data  608 A is obtained (e.g., through reading a user-supplied data or through a calculation based on the summary operation), the configuration data  118  may be continuously accessed (e.g., read) by the DMA controller  104  to continuously perform the summary operation on the configuration data  118  during the operation of the programmable device  600 . Once the current summary data  612  is ready, the comparator  614  may compare it with the master summary data  608 A. The current summary data  612  may be refreshed when a next round of the summary operation on the configuration data  118  is performed. The comparator  614  may then check the current summary (e.g., refreshed) data  612  with the master summary data  608 A. This process may continue until the comparator  614  detects a mismatch between the master summary data  608 A and the current summary data  612 . The mismatch may indicate a degradation of the configuration data in the configuration registers  118  due to many factors (e.g., soft errors). If no mismatch is detected, the above process is repeated continuously. 
     Once the comparator  614  detects the mismatch, an exception action or signal (e.g., an interrupt data, a flag, etc.) may be generated and communicated to the processor  110  of  FIG. 1  to initiate a corrective action. Based on the interrupt data, the processor  110  may initiate the reloading of the configuration registers  118  from the first memory  114  (e.g., a flash memory and/or different from the first memory  606 A) with the original set of configuration data. Alternatively, the reset  102  may be asserted to initiate a new configuration process, such as the one based on the DMA controller  104  as illustrated in  FIGS. 1 and 2 . In one example embodiment, the mismatch may flag a fatal error to the processor  110 . 
     In another example embodiment, the master summary data  608 B, a duplicate of the master summary data  608 A, may be generated. The master summary data  608 A may be compared with the master summary data  608 B (e.g., and/or with other duplicates of the master CRC data  608 A) continuously and/or intermittently using the comparator  614 . When there is a mismatch, a fresh set of configuration data may be loaded to the configuration registers  118  and/or a new set of the master summary data  608 A and the master summary data  608 B may be obtained and/or a fatal error may be communicated to the processor. 
     It is appreciated that the system to maintain the integrity of the configuration data may be transparent to the user of the programmable device  600  and/or the system may not hinder the performance (e.g., speed) of the programmable device  600  in any major way. For instance, the DMA controller  104  may assign the lowest bus priority to the system (e.g., the priority 7 on a scale of 0-7 where 7 is the lowest), such that the performance of other operations may not be sacrificed. Nevertheless, 8K bytes of configuration data may be able to perform the CRC 125 times per second when the speed of the DMA controller  104  is 100 MHz and a Priority 7 DMA is allocated 1% of the available bus clock cycles, according to one embodiment. Alternatively, the processor  110  rather than the DMA controller  104  may oversee the system to maintain the integrity of the configuration data (e.g., although this may sacrifice the performance of the programmable device  600 ). 
       FIG. 7  is a process flow chart of an exemplary process for checking the integrity of configuration data by performing a cyclic redundancy check (CRC) of configuration data, according to one embodiment. In operation  702 , the configuration data are loaded to configuration registers of the programmable device. In operation  704 , a master CRC data is accessed (e.g., from data supplied or based on a cyclic redundancy check applied to the configuration data). In operation  706 , a current CRC data (e.g., through applying the cyclic redundancy check to current configuration data) is generated. In operation  708 , the current CRC data is compared with the master CRC data. If there is mismatch, an event is generated in operation  710 . Otherwise, operations  704 ,  706 , and  708  are repeated. 
     Alternatively, redundancy check (RC) other than the CRC may be performed on the configuration data. For instance, checksums, a horizontal redundancy check, a vertical redundancy check, and a cryptographic message digest may be utilized to produce a similar result. Then, a current RC data (e.g., RC data based on current configuration data) and a master RC data (e.g., RC data based on initial configuration data) may be compared. The above process may be repeated until there is a mismatch between the current RC data and the master RC data. 
     When there is the mismatch, an exception event may be performed (e.g., such as communicating an interrupt data to a process of the programmable device or reloading the configuration registers with the initial configuration data). It is appreciated that the checksums, horizontal redundancy check, vertical redundancy check, and cryptographic message digest are well-known to those skilled in the art of signal error detection. It is also appreciated that the programmable device includes a microcontroller, a programmable logic device (PLD), a field programmable gate array (FPGA), and other types of programmable device. 
     In summary, embodiments described herein pertain to methods and systems of continuously checking the integrity of configuration data present in the configuration registers of a programmable device. The state of the configuration data may be checked with the original configuration data stored to a different location. The DMA controller of the programmable device may enable to run the error-detection operation in background without sacrificing the performance of the programmable device. 
     The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.