IC80C32 Datasheet, PDF (39/48 Pages) Integrated Circuit Solution Inc – CMOS SINGLE CHIP 8-BIT MICROCONTROLLER

IC80C52
IC80C32
ROM Lock System
The program lock system, when programmed, protects the
ROM code against software piracy. The IC80c52/32 has a
two-level program lock system (see Table 14) and a 32-
byte encryption table. No matter what lock bit is, the user
submits the encryption table with his or her code in verify
ROM mode. both the lock-bit and encryption array.
Encryption Array
Within the ROM array are 32 bytes of Encryption Array that
are initially unprogramed (all 1’s). Every time that a byte is
addressed during verify, five address lines are used to
select a byte of the Encryption 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
unprogrammed state (all 1’s), will return the code in its
original, unmodified form.
When using the encryption array, one important factor
needs to be considered, If a code byte has the value 0FFH,
verifying the byte will produce the encryption byte value. If
a large block (> 32 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
programmed with some value other than 0FFH, and not all
of them the same value.
Table 14. Program Lock Bits
LB1
LB2
Protection Type
1
U
U
No program Lock Features enabled. (Code verify will still be encrypted by the
Encryption Array if Programmed
2
P
U
MOVC instructions executed from external program menory are diabled form
fetching code bytes from internal memory, EA is sampled and latched on Reset.
3
P
P
Same as 2, also ROM verify is disabled.
Integrated Circuit Solution Inc.
39
MC002-0B