System and process for load an operating system of an information processing device

[0002] 1. Field of the Invention

[0003] This invention relates to a process for loading an operating system of an information processing device with a microprocessor such as a computer or programmable logic controller.

[0004] 2. Discussion of Background

[0005] The operating system forms the basic software, in a computer in the same way as in a programmable logic controller. It provides an environment, in liaison with the computer or PLC components, in which the application software or programs (often called “applications”) can operate.

[0006] There are information processing devices such as the PLC in FIG. 1 that are equipped with a backed up RAM memory and in which the operating system is fully or partly located in an erasable Flash EPROM memory.

[0007] The operating system is provided with a boot program for starting the device and for loading the Flash EPROM memory when the said system is updated.

[0008] This update starts by erasing the Flash EPROM, and it will be impossible to restart the device if there is a power failure before the boot program (FIG. 2) is completely loaded.

[0009] The blocking situation thus generated makes it necessary to return the device to the factory or to work on site to replace the Flash Eproms that have lost their operating system.

[0010] The purpose of this invention is to reduce the risk of losing the operating system if a mains power supply failure occurs before the boot program (by definition, the boot program is the smallest software capable of starting the equipment and loading a complete operating system) has finished loading.

[0011] The process for loading an operating system according to the invention is applicable to an information processing device comprising a power supply with an energy reserve, a microprocessor, an erasable Flash EPROM memory; a backed up RAM memory; a device for detecting mains power supply failures; a console link or mass memory for updating the operating system and it is characterized by the fact that when making an update, the operating system transfers the boot program into the backed up RAM, then executes this boot program stored in RAM, this boot program stored in RAM erasing the Flash EPROM memory and then loading the new operating system into the Flash EPROM from the console link or the mass memory.

[0012] According to one characteristic, when a mains power supply failure is detected, the reserve energy in the power supply is sufficient for the boot program to program the pointer to the entry point in backed up RAM into the Flash EPROM memory so that when mains power returns, the microprocessor starts the boot program stored in RAM at the Restart address.

[0013] We will now describe this invention referring to an embodiment given as an example and represented by the appended drawings in which:

[0014] A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed descriptions when considered in connection with the accompanying drawings, wherein:

[0015] FIG. 1 represents the external view of the update to the operating system of a PLC;

[0016] FIG. 2 illustrates the internal organization of the Flash EPROM and the backed up RAM in a loading process that does not use the invention;

[0017] FIG. 3 illustrates the internal organization of the Flash EPROM and the backed up RAM for a loading process according to the invention.

[0018] Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, and more particularly to FIGS. 1-3 thereof, there is illustrated a hardware configuration according to the present invention.

[0019] The hardware configuration shown in FIGS. 1-3 consists of a programmable logic controller (PLC) 3 and a PC or terminal type programming console 1. The PLC 3 and its console 1 are connected by link 2 through which they can communicate. The PLC 3 has a power supply with an energy reserve (i.e., backup power function), a microprocessor(not shown), an erasable Flash EPROM type memory 6, a backed up RAM memory 5, a device for detecting main power supply failures (not shown), and a console link 2. The operating system is provided with a boot program 6afor starting the PLC 3 and loading the Flash EPROM memory 6. The operating system is updated using diskette 4.

[0020] As an alternative, the configuration shown in FIG. 1 may consist of a computer 1 alone, provided that it includes the above devices mentioned for the PLC 3. In this case, the purpose would be to update the operating system of the computer 1 itself.

[0021] When an update is made, the operating system will run the boot program 6awhich starts by placing itself in portion 5aof the backed up RAM 5.

[0022] Since the copy of the boot program 5ais now in the RAM 5, it can then erase the portion 6cof the Flash EPROM 6 and load the new operating system contained on diskette 4 through the console link 2.

[0023] At the end of loading, the contents of diskette 4 will have been transferred to the Flash EPROM and the PLC 3 can restart on the new operating system.

[0024] When a main power failure is detected before loading is finished, the power supply energy reserve enables the boot program to mark the pointer to its own entry point (LD_RAM) 5bin backed up RAM 5, at the Restart address 6dof the microprocessor in the Flash EPROM 6.

[0025] Therefore, when main power is restored, the microprocessor can restart execution of the loading program stored in backed up RAM 5 in order to restart the cycle of erasing the Flash EPROM 6 and loading the operating system.

[0026] The invention reduces the risk of losing the operating system in the time necessary to erase the single-block Flash EPROM 6, or the sector containing the boot program in the case of multi-block Flash Eproms.

[0027] Obviously, the condition necessary for the invention to work correctly is that the boot program is always loaded in the Flash EPROM before the microprocessor Restart address is loaded.

[0028] Obviously, it would be possible to imagine variants and detailed improvements, or even to consider using equivalent means, without going outside the scope of the invention.