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87C51 Datasheet(PDF) 33 Page - NXP Semiconductors |
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87C51 Datasheet(HTML) 33 Page - NXP Semiconductors |
33 / 38 page Philips Semiconductors Product specification 80C51/87C51/80C31 80C51 8-bit microcontroller family 4K/128 OTP/ROM/ROMless, low voltage (2.7V–5.5V), low power, high speed (33 MHz) 2000 Jan 20 33 MASK ROM DEVICES Security Bits With none of the security bits programmed the code in the program memory can be verified. If the encryption table is programmed, the code will be encrypted when verified. When only security bit 1 (see Table 10) is programmed, MOVC instructions executed from external program memory are disabled from fetching code bytes from the internal memory, EA is latched on Reset and all further programming of the EPROM is disabled. When security bits 1 and 2 are programmed, in addition to the above, verify mode is disabled. Encryption Array 64 bytes of encryption array are initially unprogrammed (all 1s). Table 10. Program Security Bits PROGRAM LOCK BITS1, 2 SB1 SB2 PROTECTION DESCRIPTION 1 U U No Program Security features enabled. (Code verify will still be encrypted by the Encryption Array if programmed.) 2 P U MOVC instructions executed from external program memory are disabled from fetching code bytes from internal memory, EA is sampled and latched on Reset, and further programming of the EPROM is disabled. NOTES: 1. P – programmed. U – unprogrammed. 2. Any other combination of the security bits is not defined. ROM CODE SUBMISSION When submitting ROM code for the 80C51, the following must be specified: 1. 4k byte user ROM data 2. 64 byte ROM encryption key 3. ROM security bits. ADDRESS CONTENT BIT(S) COMMENT 0000H to 0FFFH DATA 7:0 User ROM Data 1000H to 103FH KEY 7:0 ROM Encryption Key 1040H SEC 0 ROM Security Bit 1 1040H SEC 1 ROM Security Bit 2 Security Bit 1: When programmed, this bit has two effects on masked ROM parts: 1. External MOVC is disabled, and 2. EA is latched on Reset. Security Bit 2: When programmed, this bit inhibits Verify User ROM. NOTE: Security Bit 2 cannot be enabled unless Security Bit 1 is enabled. If the ROM Code file does not include the options, the following information must be included with the ROM code. For each of the following, check the appropriate box, and send to Philips along with the code: Security Bit #1: V Enabled V Disabled Security Bit #2: V Enabled V Disabled Encryption: V No V Yes If Yes, must send key file. |
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