Part # Application Note Imaging datasheet

Part Manufacturer: ST Microelectronics

ST Microelectronics

Part Description: Managing the Read-out Protection in Flash Microcontrollers

Part Details:

AN1720 ® Application Note Managing the Read-out Protection in Flash Microcontrollers By DTV - Monitor MCU Applications Lab Introduction Once a MCU has been programmed with its final software, it may be protected against piracy by forbidding any further read-out of its contents. Each Flash MCU (either HDFlash or XFlash type) has this capability, by means of a freely programmable option byte, but each kind of programming tool requires a different method to enable it. The examples and procedures below are fitted for the ST7FLCD1 MCU, with an HDFlash memory array. These guidelines are applicable to any other MCU (even XFlash) but all MCU-related features, like option bytes, default values, enabled/disabled states, compiler options etc.. must be carefully reviewed and fitted for the new target MCU. 1 Read-out Protection Principle The protection against further read-out consists of a dedicated configuration bit, named FMP_R, to program to the desired value. This configuration bit is located in the Option Byte 1, as described in the Flash Program Memory chapter of the ST7FLCD1 datasheet: STATIC OPTION BYTE 1 7 6 5 4 3 2 1 0 FMP_R Default 1 1 1 1 1 1 1 1 OPT0= FMP_R Flash memory read-out protectionThe bit0, FMP_R, indicates if the user flash memory is protected against read-out piracy: 0 Read-out protection enabled 1 Read-out protection disabled By default, this bit is set to 1 (protection disabled). Once programmed to 0, the read-out protection is enabled after the next reset of the MCU. The program and data stored in the Flash program memory are then protected against read-out piracy (including a re-write protection) : the contents of the MCU can no longer be read or verified. In addition, no programming tool can bypass this protection, any attempt to do so wil result in an error message. If this protection is to be removed by reprogramming the Option Byte, the entire program memory is automatically wiped out, making it impossible to read the contents of the MCU by any means. 24 June 2003 Revision 1.0 1/12 Programming the Option Byte AN1720 2 Programming the Option Byte The Option Byte 1, where the read-out protection bit is located, is a regular Flash memory byte but does not pertain to the regular Flash program memory array of the MCU. As such, it is accessible in read and write mode by means of a separate procedure, which depends on the software and hardware tool used for programming the MCU and is completely independent of the other program memory array. The following operations describe how to program and clear this option byte on the fol owing different hardware tools: ST7 STICK tool (maker: ST) under ST7 Visual Programmer (STVP7) software tool STMC-ICC tool plugged into the ST7FLCD-EMU3 emulator (maker: ST) FLASHER ST7 (maker: Segger, Germany) The first two work under the ST7 Visual Programmer (STVP7) software tool. The last one works under a proprietary software tool.

Please click the following link to download the datasheet:

Application Note Imaging .pdf Datasheet