87C54-20 Intel Corporation, 87C54-20 Datasheet - Page 18

• Manufacturer Part Number: 87C54-20
• Description: CHMOS SINGLE-CHIP 8-BIT MICROCONTROLLER WITH 16 KBYTES USER PROGRAMMABLE EPROM
• Manufacturer: Intel Corporation

AUTOMOTIVE 87C54 87C54-20
EPROM Program Lock
The 87C54 program lock system
grammed protect the onboard program against soft-
ware piracy
The 87C54 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 4
Program Lock Bits
The 87C54 has 3 programmable lock bits that when
programmed according to Table 4 will provide differ-
ent levels of protection for the on-chip code and
data See Table 3
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-
Any other combination of the lock bits is not defined
18
1
2
3
4
Program Lock Bits
LB1
U
P
P
P
LB2
U
U
P
P
LB3
U
U
U
P
No Program Lock features enabled (Code verify will still be encrypted by the
Encryption Array if programmed )
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
Same as 2 also verify is disabled
Same as 3 also external execution is disabled
Table 4 Program Lock Bits and the Features
when pro-
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 Modes)
Reading the Signature Bytes
The 87C54 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 3 for Read Signature Byte
Protection Type
Location
30H
31H
60H
Contents
87C54
89H
58H
54H