AT80C51RA2-RLSIV datasheet(53/86 Pages) ATMEL

53 / 86 page

4188F–8051–01/08

AT/TS8xC51Rx2

TS87C51RB2/RC2/RD2 EPROM

9.1

EPROM Structure

The TS87C51RB2/RC2/RD2 EPROM is divided in two different arrays:

• the code array:16/32/64 Kbytes.

• the encryption array:64 bytes.

In addition a third non programmable array is implemented:

• the signature array: 4 bytes.

9.2

EPROM Lock System

The program Lock system, when programmed, protects the on-chip program against software

piracy.

9.2.1

Encryption Array

Within the EPROM array are 64 bytes of encryption array that are initially unprogrammed (all

FF’s). Every time a byte is addressed during program verify, 6 address lines are used to select a

byte of the encryption array. This byte is then exclusive-NOR’ed (XNOR) with the code byte, cre-

ating an encrypted verify byte. The algorithm, with the encryption array in the unprogrammed

state, will return the code in its original, unmodified form.

When using the encryption array, one important factor needs to be considered. If a byte has the

value FFh, verifying the byte will produce the encryption byte value. If a large block (>64 bytes)

of code is left unprogrammed, a verification routine will display the content of the encryption

array. For this reason all the unused code bytes should be programmed with random values.

This will ensure program protection.

9.2.2

Program Lock Bits

The three lock bits, when programmed according to Table 9-1.9.2.3, will provide different level of

protection for the on-chip code and data.

U: unprogrammed,

P: programmed

Table 9-1.

Program Lock bits

Program Lock Bits

Protection Description

Security

level

LB1

LB2

LB3

No program lock features enabled. Code verify will still be

encrypted by the encryption array if programmed. MOVC

instruction executed from external program memory returns non

encrypted data.

MOVC instruction 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.

AT80C51RA2-RLSIV 데이터시트(PDF) 53 Page - ATMEL Corporation

AT80C51RA2-RLSIV 데이터시트(HTML) 53 Page - ATMEL Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86

데이터시트 다운로드

링크 URL