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参数资料
| 型号： | AT83C5112 |
| 厂商： | Atmel Corp. |
| 英文描述： | 8-bit Microcontroller with A/D Converter |
| 中文描述： | 8位微控制器与A / D转换器 |
| 文件页数： | 71/97页 |
| 文件大小： | 1229K |
| 代理商： | AT83C5112 |
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71
AT8xC5112
4191B
–
8051
–
04/03
EPROM
EPROM Structure
The T87C5112 EPROM is divided into two different arrays:
the code array: 8K bytes
the encryption array: 64 bytes
In addition a third non programmable array is implemented:
the signature array: 4 bytes
EPROM Lock System
The program Lock system, when programmed, protects the on-chip program against
software piracy.
Encryption Array
Within the EPROM array are 64 bytes of encryption array that are initially unpro-
grammed (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, creating 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 pro-
grammed with random values.
Program Lock Bits
The three lock bits located in the CONF byte, when programmed according to Table will
provide different levels of protection for the on-chip code and data.
U: unprogrammed
P: programmed
WARNING: Security level 2 and higher should only be programmed after EPROM verification.
Table 57.
Program Lock Bits
Program Lock Bits
Protection Description
Security level
LB1
LB2
LB3
1
U
U
U
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.
2
P
U
U
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.
3
U
P
U
Same as 2, also verify is disabled
This security level is available because ROM integrity will be verified thanks to another
method.
4
U
U
P
Same as 3, also external execution is disabled.
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| AT87C5112 | 8-bit Microcontroller with A/D Converter |
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| AT83C5121XXX-PURUL | 制造商:ATMEL 制造商全称:ATMEL Corporation 功能描述:8-bit Microcontroller with Multiprotocol Smart Card Interface |
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