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參數(shù)資料
| 型號： | LP87C51FC-20 |
| 廠商： | INTEL CORP |
| 元件分類： | 微控制器/微處理器 |
| 英文描述： | CHMOS SINGLE-CHIP 8-BIT MICROCONTROLLER |
| 中文描述： | 8-BIT, OTPROM, 20 MHz, MICROCONTROLLER, PDIP40 |
| 封裝： | PLASTIC, DIP-40 |
| 文件頁數(shù)： | 16/18頁 |
| 文件大?。?/td> | 250K |
| 代理商： | LP87C51FC-20 |
AUTOMOTIVE 87C51FA/FB/FC/FC-20
EPROM Program Lock
The 87C51FA/FB/FC program lock system, when
programmed, protects the onboard program against
software piracy.
The 87C51FA/FB/FC has a 3-level program lock
system and a 64-byte encryption array. Since this is
an EPROM device, all locations are user program-
mable. See Table 4.
Program Lock Bits
The 87C51FA/FB/FC has 3 programmable lock bits
that when programmed according to Table 4 will
provide different 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.
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 it’s
original, unmodified form. For programming the En-
cryption Array, refer to Table 3 (EPROM Program-
ming Mode).
Reading the Signature Bytes
The 87C51FA/FB/FC has 3 signature bytes in loca-
tions 30H, 31H and 60H. To read these bytes follow
the procedure for EPROM verify, but activate the
control lines provided in Table 3 for Read Signature
Byte.
Location: 30H
e
89H
31H
e
58H
60H
e
FBH (for an FB part)
60H
e
FCH (for an FC part)
Table 4. Program Lock Bits and the Features
Program Lock Bits
Protection Type
LB1
LB2
LB3
1
U
U
U
No Program Lock features enabled. (Code verify will still be encrypted by the
Encryption Array if programmed.)
2
P
U
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.
3
P
P
U
Same as 2, also verify is disabled.
4
P
P
P
Same as 3, also external execution is disabled.
Any other combination of the lock bits is not defined.
16
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