參數(shù)資料
型號: AT87C54X2-SLRUM
廠商: Atmel
文件頁數(shù): 31/62頁
文件大?。?/td> 0K
描述: MCU 8051 16K EPROM 44PLCC
標準包裝: 500
系列: 87C
核心處理器: 8051
芯體尺寸: 8-位
速度: 40/20MHz
連通性: UART/USART
外圍設備: POR,WDT
輸入/輸出數(shù): 32
程序存儲器容量: 16KB(16K x 8)
程序存儲器類型: OTP
RAM 容量: 256 x 8
電壓 - 電源 (Vcc/Vdd): 4.5 V ~ 5.5 V
振蕩器型: 內(nèi)部
工作溫度: -40°C ~ 85°C
封裝/外殼: 44-LCC(J 形引線)
包裝: 帶卷 (TR)
37
4431E–8051–04/06
AT/TS8xC54/8X2
17. TS87C54/58X2 EPROM
17.1
EPROM Structure
The TS87C54/58X2 EPROM is divided in two different arrays:
the code array:16/32 Kbytes.
the encryption array:64 bytes.
In addition a third non programmable array is implemented:
the signature array: 4 bytes.
17.2
EPROM Lock System
The program Lock system, when programmed, protects the on-chip program against software
piracy.
17.2.1
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.
17.2.2
Program Lock Bits
The three lock bits, when programmed according to Table 17-1., will provide different level of
protection for the on-chip code and data.
U: unprogrammed,
P: programmed
WARNING: Security level 2 and 3 should only be programmed after EPROM and Core
verification.
Table 17-1.
Program Lock bits
Program Lock Bits
Protection Description
Security
level
LB1
LB2
LB3
1U
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.
2P
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.
4
U
P
Same as 3, also external execution is disabled.
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