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N80C58-2 数据表(PDF) 21 Page - Intel Corporation |
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N80C58-2 数据表(HTML) 21 Page - Intel Corporation |
21 / 23 page 8XC525458 ROM and EPROM Lock System The program lock system when programmed pro- tects the onboard program against software piracy The 80C5X has a one-level program lock system and a 64-byte encryption table See line 2 of Table 5 If program protection is desired the user submits the encryption table with their code and both the lock-bit and encryption array are programmed by the factory The encryption array is not available without the lock bit For the lock bit to be programmed the user must submit an encryption table The 87C5X has a 3-level program lock system and a 64-byte encryption array Since this is an EPROM device all locations are user-programmable See Table 5 Encryption Array Within the EPROM array are 64 bytes of Encryption Array that are initially unprogrammed (all 1’s) Every time that a byte is addressed during a verify 6 ad- dress lines are used to select a byte of the Encryp- tion Array This byte is then exclusive-NOR’ed (XNOR) with the code byte creating an Encryption Verify byte The algorithm with the array in the un- programmed state (all 1’s) will return the code in its original unmodified form For programming the En- cryption Array refer to Table 4 (Programming the EPROM) When using the encryption array one important fac- tor needs to be considered If a code byte has the value 0FFH verifying the byte will produce the en- cryption byte value If a large block (l64 bytes) of code is left unprogrammed a verification routine will display the contents of the encryption array For this reason all unused code bytes should be pro- grammed with some value other than 0FFH and not all of them the same value This will ensure maxi- mum program protection Program Lock Bits The 87C5X has 3 programmable lock bits that when programmed according to Table 5 will provide differ- ent levels of protection for the on-chip code and data Erasing the EPROM also erases the encryption ar- ray and the program lock bits returning the part to full functionality Reading the Signature Bytes The 8XC5X has 3 signature bytes in locations 30H 31H and 60H To read these bytes follow the proce- dure for EPROM verify but activate the control lines provided in Table 4 for Read Signature Byte Location Device Contents 30H All 89H 31H All 58H 60H 80C52 12H 87C52 52H 80C54 14H 87C54 54H 80C58 18H 87C58 58H Erasure Characteristics (Windowed Packages Only) Erasure of the EPROM begins to occur when the chip is exposed to light with wavelength shorter than approximately 4000 Angstroms Since sunlight and fluorescent lighting have wavelengths in this range exposure to these light sources over an extended time (about 1 week in sunlight or 3 years in room- level fluorescent lighting) could cause inadvertent erasure If an application subjects the device to this type of exposure it is suggested that an opaque la- bel be placed over the window The recommended erasure procedure is exposure to ultraviolet light (at 2537 Angstroms) to an integrat- ed dose of at least 15 W-seccm2 Exposing the EPROM to an ultraviolet lamp of 12000 mWcm2 rating for 30 minutes at a distance of about 1 inch should be sufficient Erasure leaves all the EPROM Cells in a 1’s state 21 |
类似零件编号 - N80C58-2 |
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类似说明 - N80C58-2 |
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