80C51 8-bit microcontroller family
4K/128 OTP/ROM/ROMless, low voltage (2.7V–5.5V),
low power, high speed (33 MHz)
MASK ROM DEVICES
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.
64 bytes of encryption array are initially unprogrammed (all 1s).
Table 10. Program Security Bits
PROGRAM LOCK BITS1, 2
SB1 SB2 PROTECTION DESCRIPTION
U No Program Security features enabled.
(Code verify will still be encrypted by the Encryption Array if programmed.)
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.
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.
0000H to 0FFFH
1000H to 103FH
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.
User ROM Data
ROM Encryption Key
ROM Security Bit 1
ROM Security Bit 2
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
Security Bit #2: V Enabled
V Yes If Yes, must send key file.
2000 Jan 20